Step 4 · Step 4: Check the Stringer Thickness

Look for the angled board on the side of your stairs that the treads and risers are attached to—that's the stringer. Measure its thickness. Knowing this helps ensure a seamless fit, especially with any side trim. Sometimes, a small piece of trim (like base shoe or quarter round) might be in the way; you may need to measure just the stringer board itself for the most accurate dimension.