Anchor Bolts

• The term "anchor bolts" refers to fasteners embedded in wet concrete floors. Builders use several types of threaded rods as anchor bolts, included J-shaped, S-shaped and straight bolts. Following a concrete pour, builders position, embed and secure bolts in the wet concrete. After hardening, the concrete securely holds anchor bolts in position and the bolts provide anchorage for load-bearing walls and other structural components. Alternatively, builders install anchor bolts into hardened concrete by drilling holes and embedding the bolts in specially formulated anchor bolt epoxy compounds.
  
  

Wedge Anchors

• Builders install wedge anchors into hardened concrete. Wedge anchors attach to concrete by gripping the sides of a predrilled hole. Wedge anchors resemble headless bolts, threaded to their tips, with roughly conical bottoms. The conical bottom, or "wedge," is hollow. Builders place the anchor's wedge at the bottom of a hole and pound the anchor's tip to crush the wedge, which expands and grips the sides of the hole. Wedge anchors are relatively strong and often are suitable for bearing heavy loads.
  
  

Concrete Screws

• Although concrete screws require a starter hole, they directly drive into concrete like wood screws into wood. Concrete screws generally require a starter hole equal in diameter to the smooth portion of the screw's shank, the portion of the shank without threads, or you'll risk cracking the concrete. Concrete screws are less expensive and easier to install than concrete anchors. However, concrete screws are weaker than anchor bolts, and concrete anchors and generally unsuitable for fastening structural components and supporting heavy items.
  
  

Powder-Actuated Tools

• Like firearms, powder-actuated tools use explosive powder to propel a material such as a nail or a spike. The powder-actuated tool's ammunition is a specially designed concrete nail. Some powder-actuated tools fire by trigger and others with the strike of a hammer to the tool's butt. These tools are expensive to purchase, but they're sometimes available for rental at home improvement stores and rental yards. While powder charges and nails are costly, their easy installation saves substantial labor and time compared with concrete fasteners that require starter holes. Although powder-actuated fasteners are strong, you should check with local building authorities before using powder-actuated tools to secure structural components, such as walls. Some municipalities ban their use.
  
  

Sleeve Anchors

• Like wedge anchors, the primary component of sleeve anchors resembles a headless bolt with a conical bottom. However, the sleeve anchor's conical tip, or "wedge," is solid, and a metal sleeve surrounds the the shank of the headless bolt. As with wedge anchors, builders insert sleeve anchors into a starter hole. When builders thread a nut onto the anchor's bolt, the nut's turning pulls the bolt upward and the bolt's wedge-shaped base splits the sleeve, causing the sleeve to grip the sides of the hole.
  
  

Drop-In Anchors

• A drop-in anchor consist of a hollow metal cylinder and corresponding bolt. One end of the cylinder is open and the opposite sealed. The sealed end of the drop-in anchor is hollow, similar to a wedge anchor's butt. Like wedge anchors and sleeve anchors, builders insert drop-in anchors into starter holes. To expand the hollow end of the anchor, builders insert a specially designed "setting tool" into the anchor's hollow cavity and punch the tool with a hammer. The hollow end splits and grips the sides of the starter hole. Once the anchor is set, builders simply thread the corresponding bolt into the drop-in anchor's cavity.