Mounting a riser rail to a wall is an instance of the general two-point fixing problem: a rigid member is located by a pair of anchors whose positions must be derived from one another rather than measured independently, because any angular error between them is amplified along the length of the rail and cannot be corrected once both holes are drilled. The governing method is to establish a single reference — one fixed anchor plus a gravity-referenced vertical line obtained from a spirit level — and to transfer all subsequent hole centres onto that line by marking the bracket itself, so the rail's alignment is inherited from a datum instead of being estimated. The concept belongs to fixings and fastenings within domestic plumbing and building trades, and combines three sub-principles: geometric datum transfer, expansion-anchor load transfer into masonry or tile, and orientation of fasteners for drainage and concealment.
Mounting a riser rail to a wall is an instance of the general two-point fixing problem: a rigid member is located by a pair of anchors whose positions must be derived from one another rather than mea…