LEATHER " YAP " EDGE COVER
It's like Marmite you either hate it or love it.
The yap edge on a leather limp cover is much wider than a normal edge and is folded down. Sometimes it meets in the middle completely enclosing the text block edges. The idea was to fully protect the Bible edges from the elements when holding in your hand whilst travelling to church. A sort of cover come bag all in one.
Having very wide turned down edges results in large pleated corners.You either hate them or love them! But they do protect the corners of the text block. Normally the Yap edge is folded tight against the text block edges. But in this case the customer wanted to leave a 5mm gap before the yap edge is folded over.