I needed two similar pieces of wood to prevent my sofa from banging against the wall and damaging it.
Cut the pieces and it was ugly and misshapen. Have a hand pane so I shaved off the jagged bits.
Miter boxes don’t help when you can’t keep a saw steady.
My issue with the miter box was I started to curve a bit and cut into the plastic. I aligned it to finish the cut and ended up with (not pictured) messy zigzag.
I got sandpaper and my hand plane out and realized the danger my fingers could be in so I clamped it up.