A central mounting hole on the front side to allow for three point mounting. This is much easier for bed leveling in comparison to 4 point mounting. First level the side with two holes and fix in place, then level the side with one hole. A glass plate is highly recommended to provide a truly flat surface and rigidity
The pads to solder onto have been greatly increased as shown in the picture. The picture shows the wires prepared for soldering routed through the holes for extra security. This does not remove the need to use proper strain relief.