Can someone please help me picture the following situation?
A lop-sided board drooped over the garden wall, announcing that it was 'to let on very reasonable terms, well furnished.
Charles Dickens, The Haunted House
There is a sign on the garden wall. The sign reads, "Furnished property for rent, reasonable terms."
Lopsided - with one side lower or smaller than the other
Board - a thin, flat, rectangular piece of wood or other stiff material used for various purposes.
Let - allow someone to have the use of (a room or property) in return for regular payments; rent
lopsided = uneven, i.e. hanging or tilted to one side. the type of board referred to was generally a piece of flat wood with the information written/painted on, this in turn would be secured to an upright post to make it easily visible, e.g. above a fence or wall surrounding the property being advertised. If the post wasn't completely upright, the board would appear 'lopsided', and would droop, or hang, over the wall.