52).

They would level off one of the side faces, and then the joint, instead of being vertical, leaned askew.

If the block had neither height nor length to spare, they made up the loss by means of a supplementary slip.

Sometimes even they left a projection which fitted into a corresponding hollow in the next upper or lower course.

Being first of all expedients designed to remedy accidents, these methods degenerated into habitually careless ways of working.