I wanted to raise my ender 3 up so I could mount everything underneath and get the center of gravity beneath the build plate. These feet use 4 mounting screws on each foot to ensure that they clamp tight and stay where you want them. They also have ridges that index with the aluminum extrusion to ensure alignment and stability. I also designed the screw holes with a counterbore that will allow any screwdriver to fit with clearance including bit drivers. To ensure the printer doesn't move and to dampen vibration it is heavily recommended to fit the feet with some form of rubber pads. Using some pieces of old shoe soles my machine is running rock steady at 150mm/s with 3k accel.

Print at 1.2mm wall thickness, 1.2mm ceiling/floor thickness, .2mm layer height, and 10% cubic infill for desired strength. I suggest printing 1 at a time as they're quite long and material intensive prints and a fail near the top with all 4 on the plate would be a hefty amount of wasted material. I used a 0.6 nozzle to help cut down time..

BOM:

16x m4x12 socket cap screws

16x m4 washers

16x m4 T nuts

4x rubber pads