This thing is a protection and mounting case for the popular 8-channel relay boards commonly sold under the SainSmart and Kootek names and by various eBay sellers.
The opening in the top of the case helps dissipate heat generated by the relays. Holes are also provided to insert wires and tighten the clamping screws without disassembly.
Assemble the case with M3x10 screws. You may wish to run an M3 tap through the holes in the bottom of the case so the screws will thread in neatly.