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Understanding Anchors

Fastener Tech Data  |  Understanding Series Introduction

Sooner or later, you may need an anchor—not a boat anchor (sorry mariners), but a way to attach a fixture to a hollow wall or maybe solid concrete.

There are many different styles available: from light duty to heavy duty; some are self drilling, others require a pre-drilled hole; you may need to supply a screw in some cases, other times you'll use an anchor that is complete and pre-assembled…just to mention a few of the differences.

Following is a list of characteristics that summarizes key features about the different types of anchors…

  • Chemical anchors require time to "cure" and cannot be installed in cold weather, but no expansion stress is caused during installation.
  • Certain anchors are reusable—they can be removed and re-installed.
  • Some anchors have machine screw threads, while others are designed to be used with wood screws, sheet metal screws, and/or lag screws. In these cases, you will most likely need to supply the screw.
  • Some anchors are pre-assembled with a screw or have a threaded stud.
  • Many anchors cannot be used for overhead applications.
  • Once installed, removing the screw will cause some anchors to loosen.
  • A few anchors are self-drilling; most require a pre-drilled hole.
  • A special tool is required to install or "set" specific anchors.
  • Some anchors require a hole that is larger than its screw size (toggle bolts for example).
  • Some anchors are removable, some are considered permanent and others are tamper resistant.
  • Anchors are often classified as light duty, medium duty or heavy duty.
  • Certain anchors are designed for hollow walls, others for solid material, and still others for hollow walls and solid material.
  • A hammer drill is sometimes recommended during installation.
  • A screw actuates some anchors, while others are gravity or spring operated.
  • A few anchors are available in long and short versions, and for use in shallow holes.
  • Bottom bearing anchors cannot be used in holes deeper than the anchor.
  • Minimum embedment depth varies with the various designs.
  • Extra depth during installation is sometimes required, like for toggle bolts.
  • Certain anchors are designed to attach the fixture during anchor installation.
  • For hollow wall anchors, be sure you are within the specified minimum and maximum grip range.
  • Some anchors are metal; others are non-metallic, making them non-conductive and non-magnetic, but certain chemicals may affect them.
  • In a few cases, the screw or the nail is the complete anchor.
  • Certain anchors are specifically rated for vibration.

Anchors fall into seven basic categories: Internally Threaded, Externally Threaded, Masonry Screw and Pin, Screw, Hollow Wall, Sleeve and Drive Anchors. Below we provide detailed information about each. Also, to help simplify your selection, refer to our handy chart…

Internally Threaded Anchors are used with machine screws, cap screws or threaded rod that you supply, and are designed for concrete, block, brick and stone (Drop-In Anchors are specified for concrete only). A setting tool may be required, and they are not removable or reusable.

Table 1. Internally Threaded Anchors.
Anchor Also Known As Description
Drop-In Anchors
Drop In Anchor
Red Head Multi-Set Drop-In Anchors, Multipurpose Expansion Anchors Designed for anchoring in concrete, Red Head Multi-Set Drop-In Anchors are internally machine screw threaded and have an expansion cone insert. A setting tool (required) drives the cone to expand the anchor inside the hole. Anchors with lips mount flush with the material's surface; if below the surface setting is desired, select an anchor without a lip. Use with cap screws, threaded rod, and other machine screw threaded fasteners. These shell type anchors can be used for overhead anchoring.
Machine Screw
Machine Screw Anchor
Calk-In Anchors Machine Screw Anchors consist of a pre-assembled internally machine screw threaded expander cone and lead alloy caulking sleeve. Use in concrete, block, brick and stone. A setting tool (required) pushes the caulking sleeve into the hole as the expander cone causes it to expand and fill the hole. Because of their short length, they are ideal for shallow holes. Use with cap screws and other machine screw threaded fasteners. Do not use this anchor in overhead applications.
Double Expansion
Double Expansion Shield
Machine Bolt Double Expansion Shields, Two-Way Expansion Anchors Using a dual expansion system, Machine Bolt Double Expansion Shields are well suited for solid concrete, block, brick and stone. They are internally machine screw threaded and expand as you tighten the screw or bolt (not supplied). Do not use in overhead applications.
Single Expansion
Single Expansion Shield
Machine Bolt Single Expansion Shields, Single Expansion Anchors Designed for concrete, block, brick and stone, the Machine Bolt Single Expansion Shield consists of an internally machine screw threaded expander cone and a set of expansion shields. Tightening the screw (not supplied) caused the wedge shaped cone to expand the shields inside of the hole. Use with cap screws and other machine screw threaded fasteners. Not for use in overhead applications.

Externally Threaded Anchors, made for concrete anchoring, have an exposed threaded stud. A nut and washer may be included, and a setting tool is not needed. They are not designed to be removed or reused.

Table 2. Externally Threaded Anchors.
Anchor Also Known As Description
Chemical Anchors
Chemical Capsule
Chisel Stud
Chemical Capsule Anchor, Chisel Stud Assembly Chemical Capsules are used with Chisel Stud Assemblies. Inside the capsule is a "synthetic mortar" that bonds the machine screw threaded stud to the concrete. Useable in lightweight and soft masonry substrates, chemical bonding resists loosening from shock and vibration. Also, no stress is created unlike anchors that require setting or other forms of expansion.
Stud Anchors B
Stud Anchor
Red Head Stud Anchor Red Head Stud Anchors are pre-assembled and consist of a bolt body and an expander end plug. Designed for concrete anchoring, they require a pre-drilled hole the same diameter as the anchor. Hammer driving the anchor causes the expander plug to expand the anchor, thus eliminating torquing requirements. This bottom load bearing design is useful in leveling and jacking applications.
Wedge Anchors A
Wedge Anchor
Wedge Anchors These heavy duty, machine screw threaded stud Wedge Anchors are designed for concrete. A pre-drilled hole, the diameter of the anchor, is required. Tightening the nut causes the tapered expansion end to expand the anchor.
Wedge Anchors B
Red Head Wedge Anchor
Red Head Wedge Anchors Available in machine screw threaded stud diameters ranging from 1/4" to 1 1/4", these heavy duty Red Head Wedge Anchors are designed for concrete applications. The diameter of the anchor is the hole size required. Because the anchor is not bottom bearing, it can be used in hole depths greater than its length. Expand the anchor by tightening the nut.
Wedge Anchors C
wej-it Wedge Anchor
wej-it Wedge Anchors wej-it Wedge Anchors are fully assembled concrete anchors that require a pre-drilled hole of the same diameter as the anchor. An exclusive feature minimizes vibration-induced wedge loosening.

Concrete/Masonry Screw and Pin Anchors are one-piece anchors used with concrete, brick, and block as noted. Concrete/Masonry Screws require a pre-drilled hole and are removable. Pins do not require a hole, and are considered permanent.

Table 3. Concrete/Masonry Screws and Pin Anchors.
Anchor Also Known As Description
Screws (Tapcon)
Concrete/Masonry Screw, Hex Head
Concrete/Masonry Screw, Flat Head
Tapcon Masonry Screws, Concrete Screws

Fasten into concrete, brick and block using Tapcon Masonry Screws. This masonry anchor cuts its own threads in a pre-drilled pilot hole. Available in Slotted Hex Washer and Phillips Flat heads. Install using Condrive tool (sold separately).

Drive Pins
Drive Pin
Hammer Drive Pins Designed for light duty, static load applications where holding strength is not an important factor, Drive Pins permanently attach fixtures to concrete and certain types of concrete block. They are installed using a standard hand tool (do not use a powder actuated tool with these pins). A steel washer near the point retains the pin in the installation tool and guides it during the driving operation. Do not use overhead.
Drive Pins
Powder Actuated
Drive Pin, Powder Actuated
Drive Pin with Washer, Powder Actuated
Ramset Pins, Ramset Drive Pins Ramset Drive Pins permanently attach a fixture to concrete or structural steel. Available in different shank lengths and with and without a washer. The washer significantly increases the bearing surface area against the material to be fastened. A plastic flute, near the point, retains and guides the pin during installation.

Screw Anchors expand when a sheet metal screw, wood screw or lag screw—as noted and not supplied—is installed. Generally, these are light duty anchors designed for use in one or more of the following materials: concrete, brick, block, stone, mortar joints, wallboard, wood, ceramic tile and stucco.

Table 4. Screw Anchors.
Anchor Also Known As Description
Lag Screw
Lag Screw Shield
Long Lag Expansion Shields, Short Lag Expansion Shields, Lag Screw Anchors Lag Expansion Shields are designed for concrete and the mortar joints of block and brick. Since they are not internally threaded, use lag screws (which are sometimes called lag bolts). Use the Short style in harder masonry to reduce drilling time; the Long style develops better strength in soft or weak masonry.
Ribbed Plastic
Ribbed Plastic Anchor
Polysets These light duty Ribbed Plastic Anchors are used in concrete, hollow block and brick, solid brick and wallboard applications. The anchor expands to grip the wall as you tighten the wood or sheet metal screw (not included).
Conical Plastic
Conical Plastic Anchor
Plastic Screw Anchors For lightweight anchoring in concrete, hollow block and brick, solid brick and wallboard applications. Fins on the ridged body prevent Conical Plastic Anchors from turning when the wood or sheet metal screw (not supplied) is installed.
Tubular Plastic
Tubular Plastic Anchor
Plastic Plug Screw Anchors, Plastic Plugs Designed for concrete, block, brick and stone, these light duty Tubular Plastic Anchors are used with sheet metal and wood screws (not supplied). The anchor expands when the screw is installed. Not for overhead usage.
Alligator Anchors
Alligator Anchor
Toggler Alligator Solid/Hollow Wall Nylon Anchors Toggler brand Alligator Anchors are general purpose anchors that can be used in most materials including concrete, wood, plaster, masonry, stone, ceramic tile, stucco and drywall. A lag, wood or sheet metal screw (not supplied) expands and compresses the anchor causing it to conform to the surface of the hole.
Plastic Toggles
Plastic Toggles
Rawl Long Poly Toggles, Rawl Medium Poly Toggles, Rawl Short Poly Toggles The Plastic Toggle is a plastic anchor designed for paneling, wallboard and solid masonry that is screw actuated (screw not supplied). Break off the outer wings when installing in solid base materials.

Hollow Wall Anchors are rated for light to medium to heavy duty loads, as specified. They have either screw or spring actuated tabs, wings or body, or a gravity operated plate, that expands behind the wall to lock the anchor in place. A few are self-drilling, but most require a pre-drilled hole. Use them in one or more of the following materials as indicated: drywall, gypsum wallboard, plaster walls, hollow doors, thin panels, wood paneling, hollow brick and hollow block. Certain styles are not removable. Of the ones that can be removed, not all can be reused.

Table 5. Hollow wall anchors.
Anchor Also Known As Description
Hollow Wall Anchors
Hollow Wall Anchor, Standard Style
Hollow Wall Anchor, Drive Style
Drill Style Hollow Wall Anchors, Molly Anchors, Molly Bolts Drive Style Hollow Wall Anchors Offering better holding power than nails and screws, these sleeve type anchors are commonly used to mount fixtures to hollow walls like drywall (wallboard) and wood paneling. Prongs under the flange pierce the mounting surface to prevent anchor rotation as its screw (supplied) is tightened. Meanwhile, inside the wall, metal strips flare to lock the anchor in place. The screw may be removed and replaced without affecting the anchor. Hollow Wall Anchors are available in two styles: Drill Style requires a pre-drilled hole. Drive Style makes its own hole as it is driven into drywall.
Self Drilling
Wallboard Anchors
Self Drilling Wallboard Anchor
One Step Wallboard Anchors, E-Z Ancor Self-Drilling Drywall Anchors These one step, one piece, self drilling anchors are designed for 3/8", 1/2" and 5/8" gypsum wallboard. Available in metal and nylon versions. The tri-cut point drills a small hole, then the anchor screws into the wallboard until it is flush. Drive the anchor with a #2 Phillips bit. Use sheet metal screws (not supplied) to mount fixtures. E-Z Ancor Self-Drilling Drywall Anchors are removable.
Hollow Wall Anchors These "T" style Hollow Wall Anchors are gravity operated. The "T" bar is positioned to fit through a hole in the hollow wall. Then rotate the anchor until the bar flips to secure the anchor.
Strap Toggles
Strap Toggle
Toggler Toggle Bolt Anchors, Never-Drop Toggle Anchors Toggler brand Toggle Bolt Anchors are similar to toggle bolts and can be used in most hollow walls, ceilings and floors including: hollow brick; hollow, cinder and concrete block; cement and gypsum board; drywall; plaster; and paneling. Installed without a screw, the wall is clamped between the wing (inside the wall) and a cap (outside the wall) connected by straps, so you won't lose the wing inside the wall when you install or remove the screw. Requiring a hole size smaller than comparable toggle bolts, they are ideal for heavy loads.
Toggle Bolts
Toggle Bolt
Slotted Mushroom Head Toggle Bolts, Slotted Round Head Toggle Bolts Toggle Bolts are used in hollow wall applications like drywall and concrete block, and are two-piece assemblies that consist of a machine screw and a spring wing toggle. To install, the wings are folded back and inserted through a pre-drilled hole. Spring action causes the wings to open inside the wall, once clear of the entrance hole. Removing the screw will cause the toggle wing to fall inside the wall. (Spring toggle wings are sold separately.)
Toggle Wings
Toggle Wing
Spring Toggle Wings (no screws) These are the same Spring Toggle Wings that are supplied with the round and mushroom head toggle bolts. Use these if yours are hopelessly lost in the wall, or if you want to select a different screw. Toggle bolts are hollow wall anchors (see Toggle Bolt listing).
Alligator Anchors
Alligator Anchor
Toggler Alligator Solid/Hollow Wall Nylon Anchors Toggler brand Alligator Solid/Hollow Wall Nylon Anchors are general purpose anchors that can be used in most materials including concrete, wood, plaster, masonry, stone, ceramic tile, stucco and drywall. A lag, wood or sheet metal screw (not supplied) expands and compresses the anchor causing it to conform to the surface of the hole.

Sleeve Anchors use a pre-installed screw or threaded stud to expand the anchor once inside the hole. Rated for heavy loads in concrete and masonry.

Table 6. Sleeve Anchors.
Anchor Also Known As Description
Sleeve Anchors
Sleeve Anchor, Round Head
Sleeve Anchor, Flat Head
Sleeve Anchor, Acorn Nut
Sleeve Anchor, Hex Nut
Acorn Nut Sleeve Anchors, Flat Head Sleeve Anchors, Hex Nut Sleeve Anchors, Round Head Sleeve Anchors, One Step Anchors, Bolt Anchors Sleeve Anchors, which includes Acorn and Hex Nut, Flat and Round Head styles, are used in concrete and masonry applications. A pre-drilled hole is required, which should be the same size as the anchor diameter. As the nut or screw is tightened, an internal expander causes the expansion sleeve to expand gripping the hole tightly. They are pre-assembled and rated for heavy loading.

Drive Anchors are tamper resistant and use a pin to expand the anchor after it is in position. Use them in concrete, block, brick and stone as specified.

Table 7. Drive Anchors.
Anchor Also Known As Description
Drive Pin Rivets
Drive Pin Rivet
Masonry Pin Grip Drive Rivets, Masonry Rivets These tamper resistant Masonry Pin Grip Drive Rivets fasten into masonry and brick blocks without special installation tools. Driving the pin flush with the rivet head causes prongs to expand inside the masonry producing a strong riveted joint.
Hammer Drive
Hammer Drive Anchor
Hammer Drive Nail-In Anchors, Drive Nail Anchors, Nail-Ins These light duty, tamper resistant anchors are used for permanent mounting in concrete, block, brick and stone. Drive the center pin flush to expand the body and lock it in place. Do not use Hammer Drive Anchors for overhead applications.

When selecting an anchor, there are several important facts to keep in mind…

  • The wall thickness must be within the grip range for certain styles. If the wall is thinner than the minimum specified, the anchor will be loose; if the wall is thicker than the maximum, the anchor may not properly lock into position. Also be aware that sometimes the thickness of the fixture must be added to the wall thickness if the anchor mounts the fixture directly.
  • To achieve rated strength, be sure that any minimum embedment requirements are met. This means that a certain length must be securely embedded inside the material.
  • Minimum installation temperature is not specified for most anchors. The base material for chemical anchors (see Chemical Capsule Anchor for Chisel Stud Assembly), however, must be at least 23 degrees Fahrenheit, or as otherwise noted.
  • Most anchors can be used immediately after they are installed. As with minimum temperature, time must be allowed for the "synthetic mortar" of chemical anchors (see Chemical Capsule Anchor for Chisel Stud Assembly) to cure.
  • Some anchors are rated for hollow AND solid walls. Don't use a hollow wall anchor in a solid wall, or a solid wall anchor in a hollow wall.
  • In many cases, the hole size required will be the size of the anchor. Occasionally, though, a larger size hole will be required—as with toggle bolts.

Whenever you're looking for anchors, look to Fastener Mart for a huge selection of quality anchors.

Fastener Tech Data  |  Understanding Series Introduction