What symbol type should I use? Plug? Slot?

The slot weld symbol is the same that is used for plug welds The symbol will not show a diameter symbol before the size however The size of the weld will be

For example, if a diameter of a hole for a plug weld is to be 6mm, the plug weld symbol will be accompanied by Ø6 on its right side, signifying

plug or slot weld Plug welds and slot welds are identified by the same symbol, except that the plug weld symbol has a diameter symbol placed on its right side Tap the card

plug or slot weld symbol Single-U butt weld 8 Single-U butt weld 9 Backing run; back or backing weld 10 Fillet weld 11 Plug weld; plug or slot weld