These lugs are an alternative to threading and poking wire directly into the opening, which can fray the wire and lead to short circuits. Touch your stranded wire to the pin and compress the barrel to create a single, solid wire that fits easily and securely into connection points.) Use a compression tool to prevent a damaged barrel and loose connection.) Compression lugs are a step up from set screw lugs when you need a physically strong connection, though set screw lugs attach to even larger wire.