This side racks are designed for the poles of an Ikea Ivar Rack. You can place small stuff on it like your 3d prints.

There are 5 versions.

One with the rack directed to the front.

Two with the racks at an 45° angle to the left and to the right.

Two sideways to the left and to the right.

You need this little metal pins that come with your ivar. You don't need to put on in every hole. Two should be sufficient. Another one to fasten the rack to the brackets. And for the Angeles and the sideways rack you need another one to connect the brackets.

i also uploaded the step-files, in case you want to make the rack bigger or need another tolerance for the holes.