Where there is no door but just a hole
this might suffice as entry or escape.
A ladder could, however, play a role
when you are not exactly in good shape.
Thinking of shapes, you should be rather thin
or else you find yourself in a tight spot
in which you simply stick when you begin
to press forward, if fit or maybe not.
People advise to think before the launch
of a bold action whatsoever,
because a sudden block can always staunch
flows of a happy ending; so be clever!