For standard version, the pins can be adjusted to bridge two holes at a 45 degree angle, whereas the other blocks are designed to work at a 90 degree angle to the system grid. The blemished version does not allow to adjust at a 45 degree angle, but works fine at 90 degrees.
A second feature as part of the EBS (Extension Block System) is that it can be combined with the tooth block to form a right angle bracket with holes oriented on its side face perpendicular to the tooth block.
