A simple inflexible, sturdy and solid small bracket usable for many purposes. Can take a good amount of weight. The screws will probably rip out from the wall before the bracket itself breaks. Printable without supports, so no wasted filament. It is a very simple item, but thought was put into the details for making it work well.
It is 30mm (1.811in) x 30mm and 20mm (0.787in) wide. Slot allows drillbit to fit for driving in the screw all the way, no need to fiddle around with thin manual screw drivers to get it in there. First version had little tool access, so I made a revised version with a nice wide slot in it.
Screws I used were 3mm x 15mm T10 countersunk screws, but whatever you have that fits will fit.
Made for printing without supports. Print laying on it's side with the three holes pointing up for maximum strength.
I used 3 layers and 20% infill since I needed some weight to be supported. With 20% hexagon internal fill you get a nice and sturdy bracket. Use whatever amount of plastic you feel you need to use.
Screws used are 3mm x 15mm countersunk screws. This item is quite tough. But as with all things made up of layered plastic you should be carefull when tightening the screws with a power tool. The screw can act as a vedge and delaminate your layers if you tighten with to much force. Especially true for ABS.