Plug welded joints are used-

Deciphering Weld Symbols, Part 2: Groove Welds plug weld vs slot weld Double-U butt weld Flat single-V butt weld with flat backing run Fillet weld Convex double-v weld Plug weld plug weld vs slot weld - Slot welds use a similar technique in an elongated hole with minimum spacing between slots of 4 times the width or 2 times the length

plug or slot weld symbol Type b» may be used for connection of plating to internal webs, where access for welding is not practicable For size of slot welds, see C600