Fixed Positioning: Check this option if you intend to always have the Parts Invoicing page in the same position on the screen when processing orders. This can be done by maximzing the Parts Invoicing window, or making it always take up the same half of the screen. Checking this option will make the order process run the best.
By not checking this option, you would need to always put your mouse in a certain spot that we will see later to make the Send to IntelliDealer option work properly, which can be more cumbersome.