In article ,
Prof Wonmug wrote:

We have a very old appliance that has an electrical cord with no
strain relief. The cord comes out of a square hole in the back. I have
replaced the original cord with one that it more heavy-duty, but it
still eventually shorts out. I'm going to go get a piece of stiff
tubing about 1" long that will fit into the hole and run the cord
through that. Is there a better idea?

There are hundreds of different sizes and configurations of strain
reliefs, and you may or may not get lucky in finding one that matches
the original closely enough to be serviceable. Put a wire tie on the
wire to keep it from pulling through the hole and go back to watching TV.