balance/ strap help

I have a Gibson Explorer that is great. The only problem is that everytime I play standing up, it slides forward on me. I have to hold it up with my left hand while I play so it doesn't end up pointing to the ground. I guess it's the balance or maybe the strap. Any ideas on how I can fix this?

I had the same problem once. I used a real leather strap, which is always a bit rough on one side. That prevented it from sliding.

All Explorers & V's have the balance problem.
Strat & Les Paul shaped guitar have perfect balance, but if you realy like the Explorer you'll have to get a rough strap..