I thought I understood this rule... but now I am not so sure. I was trying to short AMD yesterday morning and the spread was: .12 X .15 I entered my order to sell at .12 The stock traded .15 (uptick) .15 .13 .10 My understanding was that once you have the uptick you can sell at any price. Since .15 was an uptick and .13 was of some size and better than my limit of .12, I thought I should have been filled. I called my trade support department and was told that a short sale has to execute on an uptick or zero uptick and not just follow an uptick. So please... educate me.