We return now to Micky's rented room:

The landlady bought one of those sofas that converts to a bed. Not one
with a metal frame that folds in, a simpler kind where the back folds
down. I'm not sure if she bought it just so she could rent the room as
a bedroom or not, but I slep on it for 3 weeks and sometimes a wood
board near the surface made it uncomfortable, at least until I fell
asleep. . One time I actually had a sore spot 4" in diameter that
lasted all day.

So I said I needed a new bed. It's a shame because she paid $1500 for
this!

She had an unused single bed in the next room, which despite her
protestations I'm sure I could have easily moved into this one, but
there was going to be a space problem while moving the other one out
and the second one in at the same time. It dawned on me to take the
mattress only and put it on the original bed, which is double-bed
wide.

So now the bed is comfortable, but the added mattress keeps moving to
the left, so that it overhangs the bed, at the side. Every time I go
to get in it, it's at least 3" hanging over, even though I do nothing
to make this happen, not getting in it, out of it, or when I'm on it.
If I don't put the mattress back in place, the next time the overhang
is more. If I forget it has this and rolll to the edge of the bed, I
can feel the mattress bending, since there is nothing underneath it,
and about to dump me on the ceramic tile floor.

That's not likely to happen but I'm sure curious why the mattress is
moving. Anyone experience this?