I looked briefly, for a clip on filament guide that could be pushed over the plastic frame of my reprap printer. I had just been guiding the filament over the frame and letting it drag but I wanted something. I found a couple of these but in all cases the slot was parallel to the hole in the guide and while that design might print better, tt does not work for me.

So I went into Tinkercad and built one.

This is not supposed to be pretty. I made the hole bid enough for 3d filament but the slot of top that comes blocked but can easily be knifed out is for 1.75mm filament.

The point is that there are two types of filament guides. One type has to be threaded while the other iind can have the filament inserted through the top and it then protects the filament and the printer edge from friction.

This guide will serve either purpose. For a threaded guide, clean it up and make sure the guide will clip on to the edge of the plastic. For the other kind of guide, just knife out the slot that is partially formed at the top of the guide.