I just ran across this on FB where some newbie was asking about handplanes and started with "I know planes are supposed to be laid on their side", ugh!
There's much information that poo poos this idea as coming from trying to keep young students from damaging planes. Teachers thought the kids might lay them on top of another tool or something other than the wood bench thT they are designed to work on.
How many of you are still following this rule and why?