JACK- (1) A mechanical or hydraulic lifting device. (2) A hydraulic ram or cylinder.

JACKKNIFE- A tractor and trailer in such an angle that the tractor cannot move forward.

JAW- (1) In a clutch, one of a pair of toothed rings, the teeth of which face each other. (2) In a crusher, one of a pair of nearly flat faces separated by a wedge-shaped opening.

JIB BOOM- An extension piece, hinged to the upper end of a crane boom.

KELLY- A square or fluted pipe which is turned by a drill rotary table, while it is free to move up and down in the table. Also called a "GRIEF STEM."

LAGGINGS- Removable and interchangeable drum spool shells for changing the hoist drum diameter to provide variation in rope speeds and line pulls.

LAY- The direction of twist in wires and strands in wire rope.

LAY, REGULAR- A wire rope construction in which the direction of twist of the wires in the strands is opposite to that of the strands in the rope.

LEVEL- To make level or to cause to conform to a specified grade.

LIFT- A layer or course of paving material, applied to a base or a previous layer.

LIP- The cutting edge of a bucket. Applied chiefly to edges including tooth sockets.

LOAD BINDER- A lever that pulls two grab hooks together and holds them by locking over the center.

LOADER, FRONT-END- A tractor loader that both digs and dumps in front.

LOAM- A soft easily worked soil, containing sand, silt, and clay.

LOOSE YARDS- Measurement of soil or rock after it has been loosened by digging or blasting.

LOW BED- A machinery trailer with a low deck.

LUFFING- Operation of changing the boom angle in the vertical plane. See "BOOM HOIST."

LUG DOWN- To slow down an engine by increasing its load beyond its capacity.

MASS DIAGRAM- A plotting of cumulative cuts and fills, used for engineering computation of construction jobs.

MINERAL DUST- The portion of the fine aggregate passing the 0.075-mm (No. 200) sieve.

MINERAL FILLER- A finely divided mineral product, at least 70 percent or which will pass a 0.075-mm (No. 200) sieve. Pulverized limestone is the most commonly manufactured filler, although other stone dust, hydrated lime, portland cement, and certain natural deposits of finely divided mineral matter are also used.

MISFIRE- Failure of all or part of an explosive charge to go off.

MOLDBOARD- A curved surface of a plow, dozer blade, grader blade, or other dirt-moving implement that gives dirt moving over it a rotary, spiral, or twisting movement.

MUCK- Mud rich in humus.

OIL- Any fluid lubricant, but not water.

OPEN-GRADED ASPHALT FRICTION COURSE- A pavement surface course that consists of high-void, asphalt plant mix that permits rapid drainage of rainwater through the course and out the shoulder. The mixture is characterized by a large percentage of one-sized coarse aggregate. This course prevents tire hydroplaning and provides a skid-resistant pavement surface.

OPTIMUM- Best.

OSCILLATION- Independent movement through a limited range, usually on a hinge.

OUTRIGGER- An outward extension of a frame that is supported by a jack or block, used to increase stability.

OVERBURDEN- Soil or rock lying on top of a pay formation.

PAN- A carrying scraper.

PAWL- A tooth or set of teeth, designed to lock against a ratchet.

PENETRATION- The consistency of a bituminous material expressed as a distance in tenths of a millimeter (0.1mm) that a standard needle penetrates vertically a sample of the material under specified conditions of loading, time, and temperature.

PERCENT OF GRADE- Measurement of slope, expressed as the ratio of the change in vertical distance (rise) to the change in horizontal distance (run) multiplied by 100.

PETCOCK- A small drain valve.

PILE CAP- An adapter between the pile-driving unit and the upper end of the pile, used to center the pile under the pile-driving unit and to reduce damage to the upper end of the pile.

PIONEERING- The first working over of rough or overgrown areas.

PIONEER ROAD- A primitive, temporary road built along the route of a job to provide means for moving equipment and men.

POND- A small lake.

PORT- Left side of a ship or boat.

POTHOLE- A small steel-sided hole caused by traffic wear.

POWER EXTRACTOR- A unit hanging from the hoist line or block and attached to the upper end of the pile and containing within itself a member (ram) which is caused to reciprocate either by means of externally supplied air, steam, or hydraulic fluid under pressure, or by internal combustion within the unit. Upward pull from the hoisting machinery supplements the extraction forces.

POWER PLANT- The power plant (or plants) includes the prime power source (which may be an internal combustion engine or electric motor) and the power takeoff.

POWER TAKEOFF- A place in a transmission or engine to which a shaft can be so attached as to drive an outside mechanism. A power takeoff may be direct drive, friction clutch, fluid coupling, hydrodynamic torque converter, hydrostatic, or an electric generator type.

POWER TRAIN- All moving parts connecting an engine with the point or points where work is accomplished.

PRIME MOVER- A tractor or other vehicle used to pull other machines.

PROPELLER SHAFT- Usually a main drive shaft fitted with universal joints.

PSI or psi- Pressure in pounds per square inch.

PUMP, DIAPHRAGM- A pump that moves water by the reciprocating motion of a diaphragm in a chamber having inlet and outlet check valves.

PUSHER- A tractor that pushes a scraper to help it pick up a load.