These stackable pieces attach to a doors' corner to allow you to flip them in place for easy painting and then stack on top of each other for easy storage while they dry.

No supports should be required. I printed 10 sets in PLA and they have performed with no issue.

Similar tools are available commercially for an exorbitant amount of money. These ones cost roughly 60 grams of filament each, 240 per door.

These are set to use a #8 wood screw to attach to the door. The stackers have right angles protruding to allow you to easily find center of a 1&3/8" door, at 2" in from the outside.

Using the center finder means same sized doors will stack perfectly every time. Just make sure to only start the screw with the center finder before turning the stacker around to actually fasten it to the door, or the right angles protruding from the model will prevent it from spinning. This side also has finger holds to easily move the door around with a partner.

The stackers have tabs protruding from the top of it that will lock into the stackers above it. This may not be secure enough if your screws are too loose. In order for these to stack safely and securely, make sure your screws are all in snug enough that the stacker cannot bend away from the door while still being able to spin freely.

The model is also designed to stack neatly with itself for storage purposes. It could also be used as a drying rack for smaller projects by fastening dowels between the tools. I will post pictures of this application when I get a chance to use them in such a manner.

Lastly, in order to stack doors of different sized width on top of each other, the guys in the video (having trouble uploading the gif) were using a jig to line up the tools instead of the built in center finder. There's no issue with this-but make sure to place one side of your jig within 2" of one edge of the door in order to still be able to flip the door with one set of stackers remaining on the ground.

The 3mf file has a plate loaded with 2 stackers labeled door painters 1.375. These are centered at 11/16" for a 1&3/8" door. This is likely the model you will need. There is a single one of these off to the side as well as a model labeled door stacker 1.75, this model will stack in line with the others however the center finder on it is centered at 7/8" for a 1&¾" door. This would work for you if you are painting an exterior door.

https://www.printables.com/model/632007-door-stackers for STLs and the working gif