What is the primary use of a lag screw?

• A. To secure fabric
• B. To join large pieces of wood
• C. To fasten plastics
• D. To tighten metal parts

Answer: (B)

A lag screw is specifically designed for joining large pieces of wood or for securing heavy wood structures together. It features a large diameter and a coarse thread, which provides superior holding power compared to smaller screws. This is particularly important in applications where strength and stability are critical, such as in constructing decks, beams, or framing in various woodworking and construction projects.

The design of lag screws allows them to be driven into wood easily, creating a strong mechanical bond due to their thickness and the helical thread pattern. This makes them ideal for heavy-duty applications, thus reinforcing the structure effectively and ensuring it can withstand significant loads.

In contrast, securing fabric, fastening plastics, or tightening metal parts require different types of fasteners that cater to the specific material properties, making those options less suitable for the primary use of lag screws.