This is an interlocking bracket for the Plugable PS2-USB4 Desktop Powerstrip.
http://plugable.com/products/ps2-usb4

The brackets securely hold the device in place, while still allowing easy access to all outlets and USB ports.

This was originally designed as an anti-theft device for a hotel chain, but also functions nicely for home use.

You can read more about it on Plugable's blog:
http://plugable.com/2015/07/10/3d-printed-bracket-for-desktop-powerstrip

The brackets held together with a 10mm M3 screw and an inset M3 Hex Nut. To mount the bracket (especially into drywall) I recommend using #6 screws and ribbed anchor. Here are the links to these products for your convenience:

M3 Screw: http://www.homedepot.com/p/Everbilt-M3-x-10-mm-Zinc-Plated-Phillips-Pan-Head-Machine-Screw-3-per-Bag-802708/204282658

M3 Hex Nuts: http://www.homedepot.com/p/Crown-Bolt-M3-0-5-Zinc-Plated-Steel-Hex-Nuts-5-Pack-37568/202836254

Screw and Anchor:http://www.homedepot.com/p/Crown-Bolt-4-6-x-7-8-in-Coarse-Yellow-Plastic-Ribbed-Anchors-with-Screws-10-Pack-00495/100338569

1. Insert hex nuts into insets of Right piece
2. Slide powerstrip into Right piece
3. Slide on Left piece
4. Insert screw through aligned holes

Shown printed using Lulzbot Mini in PLA with 20% infill. ABS also works fine.