Research, calculator methodology & source checks

Explore the evidence

• Calculator formulas and worked examples — screen mesh, spline, door clearances, blind recesses, weatherstrip length and frame diagonals.
• Blind measuring: manufacturer instruction comparison — three different official ordering methods applied to the same illustrative opening, with a downloadable CSV.
• Door-bottom clearance variation: reproducible analysis — four fully disclosed illustrative scenarios, original calculations and a downloadable CSV; not field-test data.
• Screen-size source comparison — compare documented 1/8-inch instruction differences without conflating the reference surfaces; download the example dataset.
• Use the calculators — record your own readings; results are client-side and are not a safety or product-fit approval.

What we do and do not claim

Our calculation examples and source comparisons are original editorial work: they can be repeated from the published numbers and cited manufacturer guidance. They are not measurements collected on real homes, original field studies, independent product tests, material performance experiments or proof of energy savings.

We distinguish measured values from chosen planning allowances. A user-selected allowance is not a manufacturer tolerance. Differences in product manuals are not errors until the exact item and version are known.

Editorial accountability and corrections

These pages are issued by the MendNook Editorial Team. See our editorial roles, source-checking policy and corrections procedure. We do not imply that a specific team member personally field-tested any scenario.

Primary sources checked: 2026-11-04. Check linked manufacturer instructions again before using a number on a product order. Our materials do not supersede a model-specific installation manual or local safety requirements.