Actually, my boat, a Bristol 32, has one. I doubt it's ever been used. It couldn't be simpler. It consists of two aluminum
pipes that fit into wooden chocks mounted on the bulkheads. The canvass has tubes sewn into each side to accept the pipes. I'm away from home on business, or I'd go out to the mooring
and photograph it for you. You can just barely see the chocks on the interior
shots of the bristol 32 brochure, here. The pipe berth would be mounted over the starboard settee. Bristol32
I know, tough to see anything in these old brochures.
I already have one, which I don't use, but could easily fabricate one with some basic wood working tools and a sewing machine
. Easy as pie, and a lot less useful, in my opinion.
Great regards, Mainebristol