This is a set of wall-mount brackets for the Ikea Skadis pegboards. All of the others I could see mounted through (and using up) the holes in the board. This is designed to mount on the outside edge of each corner.

There are two elements: two fixed brackets for the base and two with sliding covers for the top. Fit the bottom ones and slot the board in. Then slide the two top covers over to lock it in place.

There are two versions of the sliding covers: with and without fixing screw holes. The fixings should really be unnecessary, but for extra security, a simple M3 countersunk self-tapping screw can be used to secure them in place.