*N.B. A detailed on-line essay by S. Finch
was the starting point for this entry.*

What is the longest ladder which can be moved around a right-angled hallway of unit width? For a straight, rigid ladder, the answer is . For a smoothly-shaped ladder, the largest diameter is (Finch).

**References**

Finch, S. ``Favorite Mathematical Constants.'' http://www.mathsoft.com/asolve/constant/sofa/sofa.html

© 1996-9

1999-05-26