J-channel: Metal edging used on drywall to give the edge a better finished appearance when the wall is not wrapped. Generally, basement stairway walls have drywall only on the stair side. J-channel is used on the vertical edge of the last drywall sheet.
jack post: A type of metal structural support used as a replacement for an old/defective supporting member that can be raised or lowered through a series of pins and a screw to meet the height required. See also monopost.
jack rafter: A rafter that spans the distance from the wall plate to a hip, or from a valley to a ridge.
jalousie window: A type of window consisting of parallel glass, acrylic, or wooden louvers set in a frame, which are locked together onto a track and controlled by a crank mechanism so that they may be tilted open and shut in unison to control air flow through the window. Jalousie windows are popular in hot-humid climates.
jamb: The side and head lining of a doorway, window or other opening.
joint: The space between the adjacent surfaces of two members or components joined and held together by nails, glue, cement, mortar, or other means.
joint cement: A powder that is usually mixed with water and used for joint treatment in gypsum-wallboard finish. Also called spackle.
joint compound: In plumbing, a material applied to threaded connections to help prevent leaks in plumbing. In carpentry, a wet gypsum material applied to sheetrock joints.
joint tenancy: A form of property ownership in which multiple tenants own a property equally. If one dies, the survivor(s) automatically inherits the property in whole.
joint trench: A trench that is shared by the electric company and telephone company; one trench dug that the electric and phone utilities drop both of their service lines in.
joist hanger: A metal U-shaped item used to support the end of a floor joist and attached with hardened nails to another bearing joist or beam.
jumpers: Water pipe installed in a water meter pit (before the water meter is installed), or electrical wire that is installed in the electrical house panel meter socket before the meter is installed. This installation may be illegal.