Is there a safe and accepted (NEC) way to splice/connect two regular
electric cords/wire where the connection is not inside a box ? I have
a need to make a number of splices with regular extnsion cord type wire
(reasonably heavy duty) and it would be much easier if there is some
type of clip on type slicer. The lights came with clip on type
plugs....is there a similar splicing clip for connecting the wires

Thanks, TR