Mitre Box for skirting board - with Fusion 360 link to re-size

Made this as I had some skirting board I couldn't find a mitre-box that would hold nicely - so thought I'd design something custom.
It's got a bar on the base, so you can hold it in a bench

STL is for the board I bought (and the width of my saw), so it's unlikely it's what you need.
Fusion 360 link is - https://a360.co/2kqbcGG
Sketch should be properly constrained, so you can adjust it for what you're trying to cut at 45-degrees.

Oh - and use ABS. DO NOT USE PLA. I tried that initially