Lag Screw

A large screw for wood with a square or hexagonal bolt head, usually driven in with an impact wrench.

Lean-To

A type of structure that has a single sloped roof and is an extension to the side of a building. There are two types: an open-type, which is a roof supported with posts, or an enclosed, which contains siding.

A structure with a single sloped roof attached to the side of a building as an extension.  Lean-tos may either be open-type (roof supported by posts) or enclosed-type (enclosed with siding).

Loft

A second story room or storage area with a sloping roof, which is supported by beams and joists. Full lofts, partial lofts and center lofts are different types of lofts used in barn construction.