What is "a plug or slot weld is what type of weld?

A plug or slot weld is a type of weld where a hole or slot is filled with weld metal. This type of weld is commonly used to join overlapping plates or to attach a plate to a member that is perpendicular to it.

Plug welds are typically used when the joint does not allow for a fillet weld, such as in a lap joint or a T-joint. In this case, a hole is drilled or punched through the top plate and the bottom plate, and the hole is filled with weld metal.

Slot welds are used when a longer weld is needed, such as in a lap joint where the plates overlap over a larger area. A slot is cut into the top plate, and the bottom plate is welded to the slot.

Both plug and slot welds are commonly used in structural steel applications and are considered to be strong and reliable welding methods.