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 a collar which has to be notched on each end and cut to a length to fit the width of the tunnel. There are two arms, which are the uprights, and which have their tops cut into wedge shapes to fit the collar -  these arms stand upright and fitted one each side of the roadway.   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 forms a wall behind the uprights. At floor level, you can see the rails for the trams to travel on and as the heading is extended, likewise are the tram rails which are joined to the last set with plates and bolts.  The rails were held down on wooden sleepers with iron spikes  "Dog Nails"  that have their tops bent over so that when driven into the wood holds the bottom flange of the rails to the sleepers.