This block can be used as a straight, corner, or "T" block. the combination block is designed just like the straight block with the addition of two V-grooves that are turned 90º running across the bottom. These grooves are set back from edge by 2” to hide the notches when they are used as straight blocks. To use the block as a corner or “T” block simply break off that chunk of concrete. Also this setback provides enough space to use liners with the form.