I decided, probably foolhardily, a while back to clean out the cupboard under our stairs and put some carpet left overs in over the boards to stop draughts etc We were happily using the vacuum over the cleared out area when my friends hand went straight through a board and up to his shoulder. On further inspection this particular board had rotted and I hoped for a simple new bit of c board could be slotted in. However on pulling out the offending rotted part, I noticed that the joist under it had been cut and a bit of tatty old softwood screwed up against the two sidedes. It looked to me as if at some time there had been a burst pipe there as a length had been replaced. It was the lead type. However instead of feeding the pipe through under the joist they had cut about an inch out of the joist and dropped it through. OK so we used a more robust piece of wood and braced the bits e with it, after all nobody is going to be jumping up and down in a cupboard, but it looked to me like the old classic of pulling the ends up to work on them and ending up with the pip on top of the joist, and then cutting a hole to pop it back. You know how wobbly lead pipe is. Total drongo obviously, but lost in the mists of time, probably around the time of the last war.
Brian