One of the four concave, triangular shaped braces which form arches from one corner to another, when joined together at the top of a structure, for support of a dome over a square structure.
Penetrating finish
Any one of a number of finishes which permeate the pores of the wood, providing protection.
Penetrating oil
Oil finish, which protects the wood without an exterior coating, by sinking into the wood surface and hardening. The oil darkens the wood, increasing the grain contrast and appears to be a hand rubbed finish, without the labor.
Penetration
(1) The depth to which something passes into another item. (2) The depth of a base welding metal to which the weld metal has flowed.
Penny
Nail size that is often noted by the letter "d" after the number. One theory on the origin of this term is that the cost of certain size nails cost a number of pennies per hundred. Therefore, a nail size that costs ten pennies per hundred would be a ten penny nail.
Penstock
A component of a hydropower plant; a pipe that delivers water to the turbine.
Pentachlorophenol
Used as waterproofing for plywood and often included as a component of shake and shingle stains and preservatives, this preservative repels water, is toxic and prevents mildew and decay.
Pentagon
A plane figure with five angles and five sides.
Pentahedron
A five sided solid figure.
Penthouse
A separately roofed structure on the top of a tall block of apartments/condominiums, or simply the top-floor unit in a residential high-rise.
