What kind of screws have square- or hexagon-shaped heads?

Lag screws are designed with larger, square or hexagon-shaped heads. This distinctive shape allows for better gripping and torque when using a wrench or socket during installation. Lag screws are typically used in heavy-duty applications, such as securing wood to wood or attaching large objects to wooden structures. Their shape accommodates significant force without stripping, making them ideal for situations where a strong connection is required.

Wood screws, on the other hand, usually have a slotted or Phillips head and are intended for use in softer materials like wood. Similarly, sheet metal screws are commonly used with metal and also feature different head shapes such as hex, but they are generally not as robust as lag screws. Machine screws are used with nuts or in tapped holes, typically having a uniform cylindrical shape with various head types, like flat or pan heads, rather than the heavier, more substantial shapes of lag screws.