Updated to V2. No supports are needed, and I removed the holes that I placed - turns out its pretty stable. I also reduced the diameter of the cross members to save filament as well as added a cutout for 16mm washer on the back side. It should auto orient correctly, but print with the big flat side face down.

The top plate file was removed, it's no longer needed and you can use the spreader without it.

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This is V1 and could use some more testing, but since I don't see anything else like it, I'm going ahead and posting. Let me know if you have any suggestions.

Printed on P1S with PLA, but PETG/ABS etc would all be fine too. The blade is replaceable if the edge gets chipped. If you do lots of walls you can just sand it down as it gets used. The “back part” is optional if you have any issues with rigidity. In fact, both the M4 and M3 holes are just there to give some connection in the corners and are optional. I printed it I feel like it's strong enough without it. In the next version I'll change it up a little to not require any inserts. I'll also adjust the cutout design to not require supports there either

The 3mf plate has supports and brim baked in for the parts that could use it. The side overhangs could use a touch of support, but I didn't use them, so I could risk the whole print to save 25 cents on supports. The print profile is built for strength, but probably a little overkill. The end result is very rigid.

For assembly you need:

2 x 1/4" - 20 threaded inserts (holes are 7mm depth)

2 x 1/4" - 20 bolts, 3/4" will work.

2 x 16mm diameter washers for the 1/4-20 bolts

Optional if you need extra strength around the corners:

2 x M4 threaded inserts (4mm depth)

2 x M4 bolts around 10-11mm length should work

4 x M3 threaded inserts (4mm depth)

4 x M3 bolts around 10-11mm