Picture courtesy of the National Museum of Wales
This collier is making a 'Collar and Arms' for extending his heading (Tunnel) What you see here is the first of a three part job. This particular part is an arm which has to be cut to a taper on the end, this fit's into a notch cut out of a collar. There are two arms, which are the uprights, and these are fitted one each side of the roadway. The collar is a piece of timber, which is cut to a length to fit the width of the tunnel, which lies on top horizontally and is notched on both ends to fit on top of the two arms. There are several examples in this picture. Once erected, which is usually three feet six inches ahead of the last set, pieces of timber of around four feet six inches long are used to go behind the uprights of the last set and this one. This procedure is called lagging, and in effect forms a wall behind the uprights. When this is done it has the effect of tightening ready for the next set. At floor level you can see the rails for the tram to travel on. These rails like the heading have to be extended every so often. A collier would make use of timbers to make sleepers for the next set of rails. The rails would be laid on top of the sleepers, joined to the last set with plates and bolts. The rails would be held on the sleepers with iron spikes with the tops bent over called dog-nails. These were driven in to hold the bottom flange of the rail to the sleepers.
