"Lisp isn't a language, it's a building material." WardCunningham used this phrase in a recent interview to describe his notion of LispLanguage. It is a figurative description of Lisp which may make it more understandable or useful.
Roof staples do remind me of parentheses, especially if you step on one ;-P
Care must be taken to face them the proper direction to accomplish what is needed. Have you noticed that two staples do a much better job of fastening than does one? This is another example of SharingOfWork.