Continuous check chairs for plain road, are of two patterns, one allowing a clearance of 1¾ in. to be used in curves of 10 chains radius, and the other allowing a clearance of 2 in. to be used in curves under 10 chains, both rails in each, case being level on top.
In sharp reverse or “S” curves in plain line work where a piece of straight line cannot be given, the junction of the two curves must be laid with check rails on both sides, each check to be laid to cover the other for a safe distance.