The message
from "Steve Walker" contains these words:

Hopefully you can now see in your mental picture that a ratchet effect is
created. Hauling on the free end of the rope will pull it through the
ascender easily, as the cam opens in that direction. When you stop
hauling, the load weight is held by the ascender as it won't allow the rope
to pass in the reverse direction.

I take your word for it that it works OK. The mental picture wouldn't
gel. I had to sketch it out to see what it entailed. [Old age dimming
the little grey cells. :-)]

One thing no one appears to have touched on is what happens should the
object being lifted jam on the way through the hatch. Unless there is
already someone else in the loft the situation would appear terminal as
there is no way to release the ascender (or for that matter the rope
ratchet that sparked this thread).

With someone already in the loft why use an indirect method that doesn't
have the advantage of magnifying the pulling force? If the object is
light enough to be lifted with a direct pull then a waist belay (capstan
effect round the waist) should give sufficient braking effect to rest
the arms while providing a position in which to lift from above and, if
terminal tiredness does intervene, allow a controlled return to square
one. (Leather gloves might be advisable).

--
Roger Chapman