Anchor

What is an anchor?

An anchor is a small device that lets a screw or bolt hold securely in materials that do not grip threads well on their own, such as drywall, plaster, brick, block, and concrete. By expanding, toggling, or bonding inside the wall, an anchor spreads the load and resists pullout so you can mount things safely without relying only on wood studs.

How anchors work

Anchors create a mechanical or chemical hold in the base material:

• Expansion: The anchor widens against the hole as the screw or nut is tightened (plastic plugs, sleeve anchors, wedge anchors).
• Toggle: Wings or a metal channel flip open behind a hollow wall to clamp against the backside (toggle bolts, strap toggles, molly bolts).
• Threaded: A hardened screw cuts its own threads into masonry or the anchor body (concrete screws, self-drilling drywall anchors).
• Bonded: Adhesive fills the hole and hardens around a threaded rod or bolt (epoxy or chemical anchors).

Common uses in DIY and home projects

• Hanging shelves, mirrors, and artwork
• Mounting TVs, cabinets, and floating shelves
• Installing bathroom accessories like towel bars and toilet paper holders
• Securing handrails and grab bars
• Fastening ledger boards, gates, and fixtures to masonry
• Attaching hooks, bike racks, and organizers in garages and basements

Types of anchors

For hollow walls (drywall and some plaster)

• Plastic expansion anchors: Simple, inexpensive plugs that expand slightly as the screw goes in. Best for light loads like small frames and hooks. Limited capacity.
• Ribbed plastic anchors: Improved grip in drywall; still for light to moderate loads.
• Self-drilling drywall anchors (metal or nylon): Screw directly into drywall without a pilot hole. Good for medium loads such as small shelves and curtain brackets. Avoid overtightening.
• Molly bolts (hollow wall anchors): A metal sleeve that expands behind the wall when set. Creates a reusable threaded insert with good holding power.
• Toggle bolts (spring wings) and strap toggles: Wings or a metal channel toggle behind the wall to spread load over a wide area. High capacity for hollow walls; ideal for heavy mirrors and some shelves. Requires a larger hole.

For solid masonry (brick, block, concrete)

• Concrete screws (often called by the brand Tapcon): Hardened screws that cut threads into a properly sized pilot hole. Good for medium loads and easy to remove.
• Sleeve anchors: A metal sleeve expands against the hole as the nut is tightened. Works in brick, block, and concrete; reliable for fixtures and brackets.
• Wedge anchors: High-strength expansion anchors for concrete only. Common for structural attachments, heavy racks, and ledgers.
• Lag shields: Lead or alloy sleeves used with lag screws; suitable for brick or block where concrete screws struggle.
• Drop-in anchors: Flush-set, internally threaded anchors for concrete; used when you want a removable bolt with a clean surface.
• Chemical or epoxy anchors: Adhesive bonds a threaded rod into the hole for very high loads or in weak or cracked masonry. Requires cure time.

Specialty and quick-fix options

• Hammer-drive or nail-in anchors: Light-duty, fast installation for clips and straps.
• Ceiling toggle anchors: Designed for overhead use; verify ratings carefully.

Choosing the right anchor

Match the anchor to the wall and the job:

• Base material: Identify whether you have drywall over studs, plaster and lath, brick, concrete block, or poured concrete. A stud finder, a small test hole, or a masonry bit test can help you tell.
• Load and direction: Know the weight and whether the load pulls straight out (tension) or down along the wall (shear). Tension is more demanding in drywall; toggles excel here.
• Weight rating and safety factor: Use the manufacturer rating for your wall type and apply a safety margin of at least 2x. For safety-critical items like grab bars, fasten to studs or concrete and consider 4x.
• Screw size and length: Choose anchors that match the screw size your hardware requires and allow full engagement without bottoming out.
• Environment: Use stainless steel or hot-dip galvanized hardware in bathrooms, kitchens, and outdoors to resist corrosion.
• Hole size and depth: Follow the packaging drill size and embedment depth. Too small can split material; too large reduces holding power.
• Edge distance and spacing: Keep anchors away from edges and corners to prevent cracking. In masonry, stay out of mortar joints and keep several anchor diameters from edges. In drywall, avoid very close placement that can crumble the paper.

Quick pick guide:

• Light decor in drywall: Ribbed plastic or small self-drilling anchors
• Medium loads in drywall: Metal self-drilling anchor or molly bolt
• Heavy loads in drywall: Strap toggle or wing toggle (or, better, find a stud)
• Brick or block: Sleeve anchor or concrete screw
• Solid concrete: Wedge anchor, concrete screw, or drop-in anchor
• High-load or questionable masonry: Chemical anchor with threaded rod

Installation tips

General steps:

1. Mark the location and use a level for anything wide like a shelf or bracket.
2. Confirm wall type and choose the correct anchor and drill bit.
3. Drill a pilot hole if the anchor requires it; use a stop collar or tape to control depth.
4. Clear dust from the hole. In masonry, use a vacuum or blow-out bulb.
5. Install the anchor per instructions and drive the screw or tighten the nut snugly, not aggressively.

Drywall toggle example:

• Drill the specified hole size.
• Insert the toggle through the hole and seat the head flush.
• Pull gently on the strap or hold tension on the screw while tightening to keep the toggle engaged.

Concrete screw example:

• Use a hammer drill and the exact bit size on the package.
• Drill to the proper depth and clear dust thoroughly.
• Drive the screw with an impact driver; stop when snug.

Wedge anchor example:

• Drill the exact diameter required, deeper than the anchor.
• Tap the anchor to the correct embedment and tighten the nut to the specified torque.

Common mistakes to avoid

• Using a drywall-only anchor in brick or concrete, or vice versa
• Picking an anchor by package weight alone without matching to your wall type
• Drilling the wrong hole size or leaving dust in a masonry hole, which reduces holding power
• Overtightening, which can strip drywall or crush the anchor
• Mounting heavy or safety-critical items only in drywall instead of fastening to studs or concrete
• Installing near edges or mortar joints where the base material is weak
• Reusing anchors that spin or have been removed; replace them and patch if needed

Maintenance and removal

• Check mounts that see vibration or movement a couple of times a year and retighten if needed.
• For anchors that spin during removal, hold light tension on the fixture or insert a small wedge under the head to bite.
• If a hole becomes oversized, toggle to a larger anchor, move the hole, or fill the area with setting compound or exterior-grade epoxy (for masonry) and redrill once cured.

Related terms

Stud, pilot hole, shear load, tension load, lag screw, wall plug, Tapcon, expansion anchor, sleeve anchor, wedge anchor, molly bolt, toggle bolt, drop-in anchor, epoxy anchor, stud finder.

Practical examples

• 30 lb framed mirror on drywall with no stud: Use a strap toggle rated above 60 lb for your drywall thickness, or two metal self-drilling anchors spaced widely. If a stud is reachable, use wood screws into the stud instead.
• Towel bar on tile over drywall: Drill the tile with a glass and tile bit, switch to a regular bit for drywall, and use metal self-drilling anchors or molly bolts. Better yet, align at least one bracket with a stud.
• TV mount on concrete: Use wedge anchors or concrete screws sized for the mount holes. Verify embedment depth and clear dust before tightening.
• Handrail on brick wall: Avoid mortar joints. Use sleeve anchors or epoxy-set threaded rod with washers and nuts.
• Garage bike hooks in ceiling joists: Skip anchors; screw directly into wood joists with lag screws. If joists cannot be hit, use ceiling-rated toggles and confirm capacity, or add a wood backing board fastened to framing.