Japanese manufacturer Hasegawa produces crazy tall ladders (up to 15' in height) with an unusual design: They feature just three points of ground contact, not four, and the base of the step side is splayed like a certain French attraction.
"The wide base, deep steps, telescopic back leg, as well as broad clawed feet and flat top make the Hasegawa Tripod Ladder incredibly safe and easy to use," the company writes. "Similar to the design of the Eiffel Tower, your weight is directed downwards and outwards, pinning the ladder to the ground."
The target market isn't contractors, installers or repairpersons:
"These aluminum tripod ladders are used all over Japan and Europe and now in the U.S., by gardeners and nurserymen. Our customers include tree surgeons, topiary specialists, institutional and estate gardeners, orchard owners, hedging contractors, permaculturists and and landscapers. Countless gardening enthusiasts appreciate the stability and practicality of the tripod design."
I'm not crazy about the fact that Eiffel kind of sounds like "I fell." But seen in use, they do indeed look pretty stable, and I believe the engineering wisdom is irrefutable: