The Scor Pal is basically a plastic board with grooves in it. The top and sides are raised so you can push the paper right into the corner and get an accurate measurement. The top portion also has a ruler along it that coincides with the grooves. The grooves are spaced every half inch from ½” to 11 ½” with special grooves at 4 ¼” (your basic A2 card fold). It also has a few other grooves at commonly used measurements and places you would score to make different projects. It also comes with a bone folder and a convenient spot to store your bone folder in the upper right corner. I got a kick out of how the bone folder clicks in and springs out when you push the button to release it (oh the little things that amuse me). I always get a crisp, accurate fold when I use my Scor Pal.
The Scor Pal retails for $39.95, but always check for stores that have or accept coupons when shopping.
Make sure you check out the ScorPal site for more info. They also have many tutorials for projects you can make with your Scor Pal.