The answer is no. Gilbert plugs are designed and manufactured to work exclusively with 18 AWG wiring. Mini lights are commonly made with 2 or 3-wire harnesses of 20 or 22 AWG wiring. Mini lights – also known as Christmas tree lights – are wired in series and cannot be cut. The bulbs are rated for a specific current draw. Modifying the length of the string violates any ratings or warranties and reduces the lifespan of the light string if it functions at all after modifications.

The better choice is to find a string of lights whose length most closely matches your project requirements or tuck the overage out of the site under a branch or eave.

Gilbert plugs are made to punch through the thick SPT-1 or SPT-2 insulation on 18 AWG Christmas light cords. SPT-1 or 2 is a measure of the thickness of the wiring insulation.