[mikethedruid]

I worked for Leviton Corporation for a number of years in their Q.C. lab as a tech. Leviton was a manufacturer of this type of replacement plug. This sort of plug came with the fiber piece to go over the exposed wiring. The slots in the fiber piece should just slide over the plug prongs, and stay in place by friction. If the piece has been removed and replaced several times, the slots can become too large. It is not absolutely necessary, but is there for safety.