This fits in to 3x 6mm (1/4") holes. Usually used round a corner.I use 9mm MDF for my borders but should easily fit in to any fairly rigid material that you can drill holes in.==2015-07-27: I have uploaded a new STL file to the correct scale!
Technical
I printed this in PLA.
If you apply a small amount of heat from a hot air gun you can shape it round a curve.