The patent pending Bloc_Loc TM technology locks onto the seam allowance and allows the quilter to square up in just seconds. There's no need for a turn-table, lifting the ruler or manually turning the block. Simply place the ruler onto the block with the seam allowance under the patent pending channel and trim the first two sides, then, using light finger pressure, simply turn the ruler around (your fabric moves with the ruler) and square up the other two sides Safe, efficient, and above all else, accurate every time Because Bloc_Loc TM locks onto the seam. Allows your fabric to move as one with the ruler as you turn it! Nothing could be more accurate, easier, faster or safer.