An elongate profile having a first portion and a second portion, the first and second portions being joined together at a first joining portion, the first and second portions being non collinear, the joining portion comprising an array of raised or rebated formations, each formation extending across the joining portion in a direction which is non-parallel to the principal axis of the profile and flat lands being provided between successive formations in an array and the pitch between successive formations in an array being from 2 to 20 times, for example from 5 to 15 times, the thickness of the flatlands.