Squaring Tool: Diagonal Check

Is your structure actually square? Two diagonal measurements tell you the truth. If they match, your corners are at 90 degrees. If they don't, something needs to move - and this app tells you exactly which corner, and by how much. HOW IT WORKS Enter the two side lengths and the two diagonals. The app compares them against the Pythagorean theorem and shows a live diagram of your structure. An animated arrow points to the corner that's off and gives you the correction distance. No trigonometry. No 3-4-5 triangle guesswork. No second person holding the tape. BUILT FOR - Deck and patio layout - Foundation and footing checks - Shed and garage framing - Wall framing and partition walls - Fence lines and posts - Concrete formwork - Tiling and flooring layout WHY DIAGONALS The 3-4-5 method only checks one corner at a time, and it fails on structures where you can't reach a clean measurement. Diagonal comparison checks the whole rectangle at once. It's how professionals have squared buildings for centuries - this app just does the math instantly and shows you the fix. FEATURES - Instant square / not-square verdict - Visual diagram of your actual structure - Animated correction arrow showing which corner to move - Exact correction distance - Works offline, on any job site - Available in English, Finnish and Swedish Free to use. Pro unlock available as a one-time purchase - no subscription, no ads. Measure twice. Build once.