Rock Drainfield 
A field containing 3/4 inch crushed stone used to drain leach lines from a septic system. 

Rock Wool 
A type of insulation, vaguely resembling wool, that is blown into the space to be insulated. The material is commonly used to insulate attics. 

Rocker Switch 
Electrical switch, which is operated by touching the top or bottom of the control plate. 

Rockwell Hardness Test 
A test used to measure the hardness of a substance. A steel ball or cone is impacted on the material and the impression is measured. 

Rod
Linear unit of measurement equal to 16.5 feet. 

Rod Saw Blade 
A slender blade coated with diamond dust or a similar material and used to cut extremely hard materials.

Roll Roofing 
Asphalt roofing material available in 3-foot wide rolls. 

Roll Welding 
Form of welding using a heat source and rollers to join two surfaces. 

Rollback 
The reduction of prices to a previous level by government control or a limitation on annual value increases, usually associated with property tax.

Roller 
1. A cylindrical device used for applying paint to walls. 
2. A cylinder used as a wheel for moving a load or item.
3. A heavy cylinder used to compress a material, such as on a steamroller. 

Roller Catch 
A type of cabinet door latch. A projection on the door is inserted between to rollers when closed, thus securing the door shut. 

Rolling Mill 
A plant producing plate or sheet products through the use of large rollers. 

Rollover Gasket 
A type of gasket that is fitted around the spigot end of a length of pipe. Often used in bell and spigot joints.

Rollover Loan 
Long-term loan with a guaranteed interest rate for a shorter period with interest renegotiated periodically, at current rates or the extension of a mature loan at current rates. Alternately, delay allowed for repayment of principal, by a bank to a debtor with financial difficulties. 

Rollover Mortgage 
Mortgage with a constant rate of interest but the loan is renegotiated or rolled over after a certain period of time. 

Roman Brick 
A brick measuring 3 5/8 x 1 5/8 x 11 5/8. 

Romex 
A trade name for a type of sheathed electrical cable. 

Roof 
Outside top covering of a building. 

Roof Deck
Plywood sheathing applied to the rafters, on which the shingles or other roofing material is attached. see also Roof Sheathing. 

Roof Drain 
A drain installed at the low spot of a roof that channels water into a drainpipe to prevent water from standing or pooling. 

Roof Drain Strainer 
A wire mesh strainer used to prevent leaves, twigs, and other debris from entering and clogging a drainpipe.

Roof Jack 
A special piece of flashing designed for installation over a vent protruding through the roof. 

Roof Pitch 
The angle or steepness of a roof. Typically expressed as a certain rise over each 12 inches of run - for example, a 6 on 12 roof rises six inches for every twelve inches of run. Also called Roof Slope. 

Roof Rise 
The vertical rise of a roof over a certain horizontal distance (run). 

Roof Run 
The horizontal distance from the top plate of the wall to the midpoint of the roof. 

Roof Sheathing 
Flat boards which are nailed to the rafters on the top of a house, to which tar paper and then shingles are attached. see also Roof Deck. 

Roof Slope 
The angle or steepness of a roof. Typically expressed as a certain rise over each 12 inches of run - for example, a 6 on 12 roof rises six inches for every twelve inches of run. Also called Roof Pitch. 

Roof Tile 
Roofing material, usually made of clay or cement. Used primarily in the south and west. 

Roof Truss 
A triangular structure used to support a roof. Multiple trusses are used to assemble the framework for a roof.

Roofer 
Professional who installs or repairs roofs. 

Roofer's Knife 
A blade with a hook shaped blade, used for cutting asphalt shingles. 

Roofing Nail 
A nail with a large head, used to fasten asphalt shingles. 

Roofing Tape 
Special tape used in patching or flashing on an asphalt roof. 

Rope 
A braided length of material, usually plant fibers, used to tie or support objects. 

Ropey 
A defective paint finish where the dried surfaces shows ridges, brush marks, or similar imperfections.