Leveling instruments, as well as all surveying instruments and equipments, have to be accorded the care and proper handling that any delicate instrument merits. Give special attention to prevent sudden shocks, jolts, and bumps, which will cause retesting of the instrument to be required. A damaged or disturbed scientific instrument, however minor, will adversely affect correct and accurate results. As a rule, a visual inspection for signs of physical damage of the instrument is to be conducted before each use. An engineers level is a precision instrument containing many delicate and fragile parts. Movable parts should, when not locked in place, work easily and smoothly. When a part resists movement, there is something wrong; if you force the part to move, you are quite likely to damage the instrument. You will also cause damage by wear if you use excessive force in tightening clamps and the like.

To ensure easy movement, keep threads and bearing surfaces on movable parts lubricated. For the same reasons, these parts have to be kept clean. Always clean the parts before oiling them. When oiling the parts, use only fine instrument oil; and do not use too much of it. An excess of oil gathers dust and also thickens, which will interfere with free movement of the parts. This is especially true in cold weather because low temperatures cause oil to congeal. In cold weather, graphite powder is a more suitable lubricant than oil.

Keep the level in its case when it is not in use and when you are transporting it to and from the jobsite. The level screws and the clamp screws should be tightened just enough to prevent motion of the parts inside the case. The instrument case is designed to reduce the effect of jarring and is strongly made and well padded to protect the level from damage. When transporting the level by vehicle, you should place the carrying case about midway between the front and rear wheels. This is the point at which the bouncing of the wheels has the minimum effect.

Never lift the instrument out of the carrying case by grasping the telescope; wrenching the telescope in this manner could damage a number of delicate parts. Always lift the instrument out of the case by grasping the footplate or the level bar.

When the instrument and the tripod are to be carried from one setup point to another, loosen

Figure 14-4.-Recommended carrying position of instrument when obstacles may be encountered.

the level and clamp screws slightly. They should be tight enough to prevent the telescope from swinging and the instrument from sliding on the footplate, but loose enough to allow a "give" in case of an accidental bump against an obstacle. When you are carrying the instrument over terrain that is free of possible contacts (for example, across an open field), you may carry it over your shoulder like a rifle. But when obstacles may be encountered, carry the instrument under your arm, as shown in figure 14-4.

To avoid the effects of sunlight, you should use a surveyors umbrella or the like. If there is any great difference between the working and storage temperature, the instrument should be allowed to adjust itself to the actual working conditions for about 15 min before observations are started.