The purpose of this part (qty 3 or 4, typically, required) is to raise the bed of a printer by about 50mm. (This is a new version to replace a previous design of mine with the same purpose -- this one is much more rigid than the previous one, particularly if printed with PETG which flexes).
Why would you want to do raise a print bed?
Because I designed a new carriage assembly for a BMG extruder, RJ45 cable connector board, and BLTouch, for the purpose of keeping the nozzle as close as possible to the MGN12H bearing slider. But it brought the nozzle so far up, that the bed on the stock FT-5 won't reach the nozzle! https://www.thingiverse.com/thing:3688067
So these bolt where the M3 screws and springs previously were before (that suspend the heated bed) and then use the old springs and screws to remount the bed to its new position 50mm higher. The are also tapped holes for additional M5 screws if you need to mount the risers more securely. The additional tapped holes are 14mm from the original bed mount holes, drill holes for those and orient them as desired if you want to use them.
The two long arms on the riser are to hold up corkboard squares (available from places such as Walmart or online) which help to keep heat from escaping from under the bed so that it heats better. Not necessary, but they do help quite a bit.
The riser is designed so that larger bed knobs will fit within if you use those (see the photos for mine). That bed knob file can be found at https://www.thingiverse.com/thing:2443198
Print in the orientation of the STL (for strength) no need to use supports.