The term "meter rate" is applicable to any method of charge for gas service based solely upon quantity, such as Mcf or therms used. Declining Block. The term "block" indicates that a certain specified price per unit is charged for all units of gas taken within specified increments of use. Reduced prices per unit are charged for all or any part of succeeding blocks of such units, each such reduced price per unit applying only to a particular block or portion thereof. Inverted. The term "inverted" indicates that an increasing unit charge will be applied to succeeding blocks of increasing energy use. Step. The term "step" indicates that a certain specified price per unit is charged for all gas taken during a billing period, the rate, or price depending on the particular step within which the total consumption falls. Straight-Line (Flat). The term "straight-line" indicates that the price charged per unit is constant, i.e., does not vary on account of an increase or decrease in the number of units.