How do I cut treads overhang to make them flush with risers?

Q: I have ripped up the carpet on my stairs, and I am going to paint them and install a runner. The risers are in poor shape and I am hoping I can use a thin piece of oak to fix that. How do I cut the overhang of the treads to make them flush with the riser below? There is no room for a straight cut. What tool do I need?

A: You could cut the bulk of the tread lip with a circular saw. The last few inches could be cut with a hand saw. There are also special blades for jig saws that allow a flush cut. I have a tool that would do it, but you aren’t going to spend $1200 to use a tool once. It’s a Fein Supercut.