So, I have a number of FramePunk display cases and I wanted to get these all lined up evenly so I created a small jig/tool to space these frames out.

To use the spacer, first glue the two halves together (I had to print the model in two half as they wouldn't fit on my printer bed in one go. You should end up with a long L shaped piece.

Now, using the first picture frame mount hole as a reference, push the nail through the hole (holes go against the wall). Use a spirit level on the top shelf (the smaller side without the nail holes) to level up the jig. Once you have the spirit level level, push the next nail into the other hole (you can also use a thin pencil) to make a mark. Remove both nails. Put a nail into the mark/hole you've just created. You can repeat for as many frames as you have.