Anyone Know What This Old Notched Ladder Was Used For?

Question

http://i277.photobucket.com/albums/kk80/besunny/Ladder6ftboattoppart.jpg

Found it in the garage of a deceased relative. He was a boat owner so I assumed it was a boat ladder. But no, a shop that sell boats tells me it isn't; for one thing the round rungs are tough on the bare footed boaters.

It is notched on top as can be seen. It is only 11" wide. And about 6 ft high. No writings or markings on it to help identify.

Could it be an old library ladder, for reaching high shelves? (But what's the notch for?) And old firehouse ladder (but too narrow).?

Got me stumped,. Best Answer to most logical, and especially if a link showing a duplicate or near diupe of this ladder!

Answer 1

The notch is for another ladder to be attached to to make a longer ladder. Notches into the wing-nuts. These are still used for window washing.

Answer 2

the only other ladder i have seen that was close to this was for picking fruit in an orchard..