@cstross
Picking scabs (it's that sort of night) ...
Elizabeth went to sleep with a razor-edge letter opener under her pillow, and had to explain a shredded pillow (minor) and mattress (much more expensive) next morning.
She maybe had it in a sheath?

[When I'm feeling paranoid, I keep a runguu (skull piercing mace) beside my bed. Also makes joints multidirectional.]