In nearly all styles of architecture the better class of buildings have the arch ring moulded. In Gothic and Romanesque work a projecting moulding called a "label mould" is generally placed at the back of the arch. When not very large it may be cut on the voussoirs, but usually it is made a separate course of stone, as shown in Fig. 104. When this is the case the depth of the arch ring without the label mould should be sufficient for stability.
The label mould may be cut in pieces of the same length as the voussoirs, or the joints may be made independent of those in the arch.