Back in the day, I had a house that had an old-fashioned fuse box, (not these new-fangled circuit breakers). Occasionally, I'd be out of fuses so would have to use a field expedient (like a penny under the fuse). If you find yourself without fuses, here is a handy expedient guide to help you with your selection.
Boned Jello. I don't necessarily recommend these fise expedients, but I'm sure they'd work until your house burned down.