The large calibre trench-mortars, or "Yon Minnie Wafers," as the Jocks styled them, do not so much damage breastworks as remove them. They frequently leave in a place where breastworks once stood nothing but a deep crater, with two feet of water in it. In this case the result was that, in spite of a vast amount of work carried out on the consolidation, the sector was still far from completed when the Division was relieved. In those days there was little with which to reply to trench-mortars. Appeals to the artillery for retaliatory shoots would seldom be answered, owing to the restrictions placed on the use of ammunition on account of its scarcity. Mountain-guns, manned by the R.G.A., were, however, employed, and also a form of trench howitzer; but these were inferior weapons when compared with the formidable mortars of the Germans. The Laventie front was in character similar to the Festubert front. When the Division took over the line, the defences consisted of little more than a single line of breastworks. Behind this, some 200 to 400 yards in rear, lay a series of detached supporting posts at intervals of from 300 to 500 yards. A reserve line composed of similar posts lay 1000 to 1500 yards in rear of the supporting posts. The enemy was occupying the lower slopes of the Aubers Ridge, from which he overlooked all the country in which the British defences were situated. Each sector has, as a rule, its particular "unhealthy spot." In the Laventie sector Red Lamp Corner occupied this rôle. The front line ended in a butt-end, some 100 yards from the German line at Red Lamp Corner (Point B on the diagram); 300 yards west of Red Lamp Corner the front line started from another butt-end (Point C). These two butt-ends were connected by a fire-stepped communication trench (C--E). See diagram. [Illustration: Trench Layout] The corner took its name from a red lamp which was lit at dusk and placed at B to prevent the troops garrisoning CD from shooting into those garrisoning AB in the dark. The trench from E to C was continuously subjected to close-range rifle and machine-gun fire in direct enfilade, and both it and the corner itself were places to be avoided. In these days the red lamp was a necessary precaution, as a form of activity which came later to be known as "wind fights" frequently occurred. A post would see or imagine it saw an enemy patrol, which it took to be a prelude to an attack. It in consequence opened rapid fire. This fire was taken up by posts on its right and left. Subsequently the alarm travelled for several miles, and rapid fire was opened all along the line. The fight, often occasioned by Private X., just out from home, mistaking a pollarded willow for a German, involved an enormous expenditure of ammunition, in which the shooting was not always under complete control. It will be easily understood that, without the red lamp, CD might have made things very unpleasant for AB in these circumstances.