The tool checks three real-world maneuvers, easiest first:

1. Drops in flat — unit goes straight through the hatch lying on a face, no tilt.
2. Tilt & lower — hold the unit at a fixed angle directly over the hatch, then lower straight down. Useful when the unit is too tall to stand straight but its tilted cross-section still fits.
3. Edge-pivot — like tipping a fridge into a basement. Rest one short end on the hatch lip and let the unit pivot through. The leading end drops into the crawl while the trailing end swings high above the floor. Best for tall units through a tight hatch.

If none of the three work in any orientation, the unit won't fit.