Some oil drums have filler holes at one end of the drum, so you can only use the other end of the drum to make a pan. This type of drum is ideal for making background pans, as most (or all) of the drum is required to make a pan.
If the drum has a hole in its side, you need to seal the hole. This can be done by using a threaded metal plug or by welding a piece of metal over the hole. However, if the hole is not sealed tightly or welded correctly, a rattling sound may occur when playing the notes.
Alternatively, these drums are ideal for making frontline and mid-range pans, as you can use both ends of the drum to make two pans. Cut across the middle of the drum and cut away the part of the drum where the hole is at the same time to get two pans.