Perpend stone
![The bond stones seen on the end of the right wall extend across the width of this tall, battered, dry-stone wall. Attribution: Humphrey Bolton](/Images/godic/202502/02/Footpath_at_Nab_End,_Longwood_-_geograph.org.uk_-_4685893120.jpg")
Perpend stone (parpen, parpend, perpin, and other spellings), bond stone, or tie stone is a structural element building term used by stonemasons and brick masons. Perpend is also a piece in brickwork also called a cross joint or when extending through the entire wall a transverse joint or perpend bond.