Head Jamb 
Also called a yoke, it's the upper horizontal finish member in a window frame. 

Head Joint 
Joint between the ends of two masonry units. 

Head Plate 
Also called a wall plate, this horizontal structural piece is anchored to a masonry wall. Other structural pieces may be supported from it. 

Head Pressure 
Maximum amount of pressure against which a pump can move fluid. 

Header 
1. A beam running perpendicular to the studs or joists to which joists are nailed in framing of stairways, chimneys, etc. 
2. Top horizontal piece, often made of boards nailed together, which serves as the top section of a window or door. 
3. Horizontal framing member to which the ends of the joists are nailed. 
4. A short section of brick or a brick laid so the end is to the wall surface. 
5. Also, a masonry unit that ties together different vertical masonry sections. 

Header, Blind 
Brick header that is concealed. 

Header, Clipped 
Also referred to as false header, brick is cut, up to half its size, to set up a pattern. 

Header or Heading, Course 
Course of brick which is set with the end of the bricks facing outward. 

Header Flare 
Exposed header, which is painted noticeably darker than the others. 

Headroom 
1. Any amount of vertical clearing. 
2. Space or clearing overhead, as in a doorway, etc. 

Headstock 
1. A bearing or support for a revolving or moving part of a machine. 
2. The part of a lathe, which supports the spindle, which holds and turns the work. 

Hearing 
A formal procedure, with issues of fact or law to be tried, in which parties have a right to be heard. Similar to a trial with the possibility of a final order. Hearth The stone or floor of a fireplace, which often extends into the room and is either flush with the floor or raised. Hearth Stone 1. The stone that forms the hearth of a fireplace. 2. A soft stone or powdered composition, which is used for cleaning a hearth, steps, etc. Heartshake Disintegration and splitting, which forms across the growth rings of a log whenever rot, exists at the center of the log. 

Heartwood 
The wood of a tree that reaches from the pith (the soft core or center) to the sapwood (where cells have hardened). This wood may contain phenoloic compounds, gums, resins, etc. making it darker and more decay resistant. Redwood is an example of a wood that is used specifically for its durable qualities. 

Heat Absorbing Glass 
Window and skylight glass that contains iron to absorb heat, thus reducing the heat transmitted through the glass. 

Heat Collector 
Also referred to as a solar collector or solar panels, it collects heat from the sun, which is turned, into energy that is used most commonly to heat water for the home or pool. There are different forms of collectors. 

Heat Exchanger 
Apparatus, which transfers heat from one fluid to another in cooling or heating systems. Air conditioners use both a condenser and an evaporator. Steam and hot water radiators are heat exchangers, which are used to produce heat. 

Heat Gun 
Device, much like a hair dryer, which changes electricity to heat with a blower to aim that heat at a surface, to soften paint for removal or to accelerate drying. 

Heat of Fusion 
Heat needed to melt a particular solid. For example, gold becomes liquid at about 2,000 degrees F and iron at 2,730 degrees F. 

Heat of Vaporization 
Heat needed to turn a liquid into a gas. 

Heat Pump 
Apparatus that can heat but also cool by changing its cycle and using a refrigerant, a compressor and heat exchanger. 

Heat Sink 
Often used in electronics where it is necessary to keep heat from sensitive circuit parts during soldering, this metal shape has good heat conductivity to draw heat away from an area. 

Heat Transfer 
Heat movement from one object, one place or fluid to another. 

Heat Treating 
Enhancement of a material by use of heating and cooling rates. 

Heat Welding 
Heating process, which can fuse plastic pipes and fittings together or to seal roofing membranes together. 

Heater, Baseboard 
Heating unit installed along the baseboard. 

Heating Cable 
Cable, often in a plaster ceiling, used to generate heat by use of electrical resistant, which occurs when an electrical current passes through a conductor with high resistance to the flow of current, which converts the electrical energy into heat. 

Heating, Ventilating, and Air Conditioning (HVAC) 
Regulation of temperatures, through heating and cooling, inside of residential and commercial building. 

Heave 
1. To raise or lift with effort or to cause to be lifted. 
2. The extent of horizontal displacement caused by a fault in the earth. 

Heavy Timber Construction 
Use of heavy timbers, connected with bolting and metal plates at their intersections, for main structural pieces in construction. The heavy timbers carry the structural load so that studs are added to form partitions and not for weight bearing. 

Heavyweight Concrete 
Used for radiation shielding, the concrete is made dense by addition of a heavy aggregate. Regular concrete weighs approximately 150 pounds per cubic foot while heavyweight concrete weighs 400 pounds per cubic foot. 

Hectare 
A measurement, equaling 2.471 acres or about 107,637 square feet or 10,000 square meters. 

Hectogram 
Metric unit of weight, which equals 100 grams or 3.527 ounces. 

Hectoliter 
Metric unit of volume, which equals 100 liters or 26.4 gallons.