B-O, that is the front end, you short 2000 at $5 and have to cover at $10. But you don't have the cash ($10K) from the sale (folks don't usually have proceeds sitting in their account), and now you have to find $20K, so the broker sells other stock you own, and if they have gains in those stocks, then they have a tax situation, if it happens in the next 4 days. Hope that happens.