Yep, what Jason said. It allows you to print and check register to base plate or keyline. Not in Register? Wipe off plastic, registartion adjust, print again. This is a whole lot quicker than putting on a new piece of fabric or scrap shirt on when you want to see if the print is in register. Note that I leave 2 pallets with shirts printed and no plastic. (BTW having the same brand and color as the order really helps, tough to go from a 4.8oz low end during set up to a 6.1 oz high end ringspun without having to go back and adjust squeegee pressures), no pla. Once the first with plastic is in reg you can print on the actual base plate which also allows you to check color on top of the base. Note I put 2 plastic covered images followed by 2 with just the base, no plastic. This is done to allow your workers to leap frog each other or set up 2 screens at once with 2 set up workers. One other area of set-up not mentioned was the time it may take for a sim process job to wet the bottoms of all screens so that color, final halftone look, or for the registration to finalize.
