When I was at a recent ferret show, I noticed that almost all
cages had hammocks in them, and that that seemed to be the
overall favourite resting place of the ferrets.

They were of many differnt sorts, from heavy canvas ones with
metal eyelets fastened to the roof with releasable hooks to
towels strung up between the walls. Some where taut, some sagged
deeply.

When I came home, I took out the dividing floor in the transport
cage I put there to increase the floor space and tied one of my
neckkerchiefs there instead, using the ventilation holes.

It's now become the favourite secondary resting place.
Previously, when I visited my parents they would sleep under a
couch or somewhere, but not it's the hammock always. When we're
at home they sometimes stay there as they can get a better
overview of what I do than from under the bookshelf.