Used to eyeball every miter cut with a speed square, now I sneak my 10 inch sliding miter in the truck for trim
For the first 4 years of trim work I just marked with a pencil and cut freehand with a circular saw, and my corners always needed a swipe of caulk to hide the gap. After a guy in Fresno let me borrow his sliding miter for a 12 piece window casing job, I bought one that same week and my joints close up tight off the saw. Kinda feel dumb about all those tube after tube of painter's caulk, anyone else hang onto the old way way too long?
Wasted about six tubes of caulk over two years before admitting my speed square wasn't the problem, I was. Still keep the caulk in the truck though, just in case my ego needs backup.