This block has 4 holes on top two pins on the bottom. The pins are set so that by flipping the block 180 degrees, you can adjust the end of the block by 1”. The adjustment of the fence pin allows various configurations like right angles, T Shapes, and continuous fences to be constructed on the table.
The wall of the fence pins provide plenty of space to set your material against and use with clamps.
The fence pins also feature 3/4” diameter blind holes on top that can be used as a system hole for elevating clamps or stacking blocks.