2. The proper location for the meter should be one where there is no vibration. When this location has been selected, nail or screw upon the walls, a board somewhat larger than the dimensions of the back of the meter, and upon this board hang the meter by the top hanger. 3. After hanging the meter, open or remove the case or cover, and if necessary, put the mechanism in order according to instructions furnished by the manufacturer. 4. In order to operate satisfactorily, the meter should hang plumb, so that the spindle of the revolving element will be vertical, and the horizontal planes through the armature and retarding disc will be level. Many complaints relative to meters being slow on light loads, are invariably due to the fact that the meters have been installed out of plumb[B]. 5. In making the circuit connections, be very careful that the _positive_ lead or wire is placed in the _positive_ binding post of the meter. This precaution is essential for insuring an accurate and sensitive measurement on small loads. 6. When a meter of the commutated motor type sparks at the brushes at starting, it is an indication that the commutator is dusty. Clean it with a piece of closely woven cotton tape 1/4-inch in width. 7. Meters should never be allowed to remain with their covers off, in the testing room, station, or any other place. In order to get the best service, and to give them long life they must be kept clean. [B] NOTE.--The most practical and accurate method of plumbing a meter is to level it by means of a small brass weight placed upon the retarding disc. Place the weight upon the front or back upper surface of the disc, close to the edge. If the disc and weight rotate toward the right, move the bottom of the meter in the same direction so as to raise the disc on the right. When the disc is level, the weight and disc will remain stationary when the weight is placed on either the front or the back of the disc. Next, place the weight on the disc close to the edge on either side. If the disc rotate towards the front, swing the bottom of the meter away from the wall or board until the disc remains stationary when the weight is placed upon it on either side. If the disc rotate toward the back, raise it up on that side by bringing the top of the meter away from the wall or board. It is possible that the second levelling operation will alter the position of the disc obtained by the first operation, therefore, the first should be repeated, and after that the second also, until the disc remains stationary when the weight is placed at any point upon its surface. This method of levelling is more reliable than any method in which a spirit level is employed.