Simple shelf bracket Dimensions: 100x100x20 [mm] 75x75x15 [mm] 50x50x10  [mm] Test print 100x100x20 [mm] with PLA, 1 mm wall thickness, 50% infill, holds 10 kg load safely (that's for a pair of brackets). Didn't test the load limit jet but for heavier loads use 100% infill or stronger material like ABS, PETG...