MEASUREMENT OF DISTANCE 
11 
broken tape can generally be repaired on the ground if there 
are at hand a punch, a piece of another tape, and some pins 
to serve as rivets. 
3. Marking Pins 
Woodsmen frequently manufacture their own marking 
pins of wood or wire. Those bought from dealers are 
made of heavy iron wire, are some fifteen inches in length, 
with one end sharpened and a ring turned in the other for 
convenience in handling. Strips of cloth are tied in the 
rings, so that they can be readily seen. It is most con¬ 
venient to use eleven pins in chaining. One of them is 
stuck at the starting point, the leading man takes ten, 
and thus there is always one in the ground to start from 
when the tallies are finished. 
4. Chaining Practice 
Chains are standardized in length at about ten pounds 
pull with their full length supported. In woods work it is 
generally necessary that the chain should be suspended 
above the ground and not lie upon its surface. Care must 
be taken, therefore, in accurate measurement, to give it 
proper tension. What tension is proper for a suspended 
chain, — in other words, what sag should be allowed to 
compensate for the stretch of the chain under the greater 
tension — may be determined on perfectly smooth and level 
ground, and this is a valuable exercise for inexperienced 
chainmen. 
In order to get true chainage between points, the chain 
should be kept straight and free from kinks. It must also 
be kept in approximately true alignment, though a con¬ 
stant error of 1° in that matter, equivalent to seven inches 
error in setting pins each two rods of distance, shortens 
the line by only nine and a half inches in the mile. Simi¬ 
larly, the chain must be levelled so as to give distance in 
a horizontal line, not following the contour of the ground. 
In this last connection, that is, in getting distance correctly 
on slopes and over rough ground, are met the greatest 
difficulties in practical chaining. What is necessary is 
first, to determine when the chain is level, and second, to 
