Prof Wonmug wonmug moo.gov 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?

If you're good with hot melt glue, you can make strain relief for
plugs with that. As always, clean the parts and make sure they get
very hot.