Here's a blind-friendly tip from a Wood smith video for checking that your table saw blade is set exactly at 90 degrees.
Just take a thick block of wood, say 2 by 2 or so, and make a crosscut. When you reposition the cutoff against the rest of the piece it will fit perfectly regardless of the tilt of the blade. To check if the blade is 90 degrees just rotate or roll the cutoff 180 degrees forward and reposition it against the stock. If the blade is exactly 90 degrees there will be a perfect fit. If the blade is off even as slight as one-half of a degree, the gap between the two pieces will be noticeable and you will be able to feel it easily with your finger or fingernail.