I tried searching the archives, but didn't find anything, so figured I'd ask
here.

I have some precut stringers, and I've noticed that the routered slots for
the treads taper from about 1 3/8" in the rear to a 1" bullnose front. Can
anyone tell me why it's tapered? And also, how would I go about putting the
treads in? I assume they need to be wedged from underneath the tread
somehow? Thanks for any info!