Sewing line edge distance validator

Hi,
I made those to check the distance of my sewing lines from the edge in case I didn't use a guide. Or to make a quality control at the end of my sewing process.
I use this in leatherwork but it can be applied to other things I guess.
Also, the opening window of the tool is 1cm long which can be also use to see how many stitching holes for 1cm.