Robust camera tracking for augmented reality based on planar homographies

A device for accurately laying bricks comprising a frame positionable on a previously laid course of bricks or a wall base, a maintained in position by means of clamping devices. The device may be used for building single or cavity walls. Means are provided on the device for ensuring accurate positioning of the bricks in the horizontal and vertical planes, and for pointing the horizontal and vertical joints between the bricks.