RE:JustinLawghost block or a sell wall is set up by money managers that have alarge positions int eh company and are LONG on the stock. They are basically hundreds of thousands of shares that are set to sell at a specific price, usually major makers like full dollar amount, like 13, or half dollar amounts like 13.50.
Advanced traders with access to level 2 information can see it, those who are usuing simple quote systems wont be able to. Once the price moves up to see it, most retail traders will basically sell right below that number as a sell order above it wont likely get filled.
the price usually comes close to the sell wall and then bounces lower allowing fund managers to accumulate more and more shares at lower prices as retial investors beleive that the price wont move past that wall.
the only way to tell if it acutally is a wall is if the shares actually get sold. If they do, then it was just someone selling or could be a massive amount of traders setting that mark as their specific sell target.
if the shares magically dissapear than it 100% a sell wall or ghost block. As i wrote this, the sell wall was actually sold.. must not have been a sell wall and may have actually have been just traders from this morning who left to work with their sells at 13.50 which originally where it was.
good luck.