Inside Measurements by Overlapping Tapes
Adding two tape readings that meet at a round number to read a wall-to-wall span exactly.
Subtract Fractions by Folding the Tape Measure Back on Itself
To take 2-3/8 off of 24 without doing fraction math, fold the tape back on itself so the blade doubles over at 24, find 2-3/8 on the returning blade, and read straight across: 21-5/8. The fold turns subtraction into reading two aligned numbers.
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The Problem
"Cut it to 24 minus 2-3/8" is a borrow-the-eighths problem done on a ladder, in your head, with the saw running. Fraction arithmetic is where sixteenth-inch errors come from.
The Technique
- Pull the tape past your starting number and fold the blade back on itself, so the fold lands exactly at the starting measurement — 24" in the demo.
- On the folded-back section of blade, find the amount you're subtracting — 2-3/8".
- Read the number directly across from it on the lower blade: 21-5/8". That's your answer, no arithmetic done.
Second example from the video: start at 19-1/4", find 2-3/4" on the fold-back, read across — 16-1/2".
Pro tip: It works because the folded
blade counts the same distance in the opposite direction — every pair of
aligned numbers sums to the fold point. Which means the same fold answers
"what's left if I take X off" and "what do two pieces adding to 24 look
like" in one read.
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