Apex/Peak:  The uppermost point of a truss.

Axial Force: A push (compression) or pull (tension) acting along the length of a member.  Usually measured in pounds, kips (1,000 lbs.) or tons (2,000 lbs.), or metric equivalent.

Axial Stress: The axial force acting at a joint along the length of a member divided by the cross-sectional area of the member.   Usually measured in pounds per square inch.

Battens/Purlins: Timber sections spanning trusses to support roof covering.

Bearing:  A structural support, usually a wall that occurs at the top or bottom chord or between the end points of a roof or floor truss.

Bending Moment: A measure of the bending effect on a member due to forces acting perpendicular to the length of the member.   The bending moment at a given point along a member equals the sum of all perpendicular forces, either to the left or right of the point, times their corresponding distances from the point.

Bending Stress: The force per square inch of area acting at a point along the length of a member, resulting from the bending moment applied at that point.  Usually measured in pounds per square inch or metric equivalent.

Bottom Chord: A horizontal or inclined (e.g. Scissors Truss) member that establishes the lower edge of a truss,  In a conventional system, this is the ceiling joist.

BOTTOM CHORD BEARING: Term usually used to describe the bearing condition of a parallel chord truss that bears on its bottom chord.

BRIDGING: Wood or metal members that are placed between trusses and joists in an angled position intended to spread the loads.

BIRDS MOUTH CUT: A long notch at the ends of a member to allow for an overhang "over the wall height" less than the width of the member.

Butt Cut:  Slight vertical cut at the outside edge of truss bottom chord made to ensure uniform span and tight joints - usually 1/4 inch.

Camber:  An upward vertical displacement built into a truss bottom chord to compensate for deflection due to dead load.

Cantilever:  Extension of the bottom chord beyond its support, exclusive of overhang.

Check:  A lengthwise separation of wood fibers, usually extending across the rings of annual growth, caused chiefly by strains produced in seasoning.

Clear Span:  Horizontal distance between interior edges of supports.

Combined Stress:  The combination of axial and bending stresses acting on a member simultaneously, such as occurs in the top chord (compression + bending) or bottom chord (tension + bending) of a truss.

Concentrated Load: Superimposed load centered at a given point (e.g., roof-mounted air conditioner, furnace).

Connector Plate:  Pre-punched metal toothed connectors located at the joints and splices of a truss and designed to hold the forces which occur at those locations.

Cripple Rafter:  Infill rafter installed to continue the roof line - fixed to valley board in valley construction.

Dead Load:  Any permanent load such as the weight of roofing, flooring, sheathing, insulation or ceiling material, as well as the weight of the truss itself.

Deflection:  Downward vertical movement of a truss (when in place) due to dead and live loads.

Design Loads:  The dead and live loads which a truss is engineered to support.

Engineer Certified Drawing: A truss design where loading requirements, lumber species, sizes, grades and connector plate requirements are detailed and a certified engineer's seal is affixed.

Girder Truss: Usually a multiple-ply truss designed to carry other trusses over an opening.

Heel: Point on a truss at which the top and bottom chords intersect.

Heel Cut:  See Butt Cut.

Jack Rafter: Infill rafter installed to continue the roof-line - fixed from wall plate to hip board in hip end construction.

Joint:  See Panel Point.

Lateral Brace:  A member placed and  connected at right angles to a chord or web member of a truss.

Level Return:  A lumber filler placed horizontally from the end of an overhang to the outside wall to form a soffit.

Live Load:  Any loading which is not of a permanent nature (e.g., snow, wind).

Moisture Content of Wood:   The weight of the moisture in wood expressed as a percentage of its oven dry weight.

Overall Rise:  Vertical distance from bottommost part of the bottom chord to uppermost point on peak.

Overhang:  The extension of the top chord of a truss beyond the heel, measured horizontally.

Panel:  The chord segment defined by two adjacent joints.

Panel Length:  The centerline distance between joints measured horizontally.

Panel Point:  The point where a web or webs intersect a chord.

Peak:  Point on  truss where the sloped top chords meet.

Pitch:  Inches of vertical rise for each 12 inches of horizontal run.

Plumb Cut:  Top chord end cut to provide for vertical (plumb) installation to fascia (face trim board).

Plumb Rise:  Vertical overall measurements at the end of a truss where the top and bottom chords meet.

1/4 Point:  Point on triangular, Fink or Howe truss where the webs connect to the top chord.

1/3 Point: Point on triangular, Fink truss where the webs connect to the top chord.

Purling:  A horizontal member attached to and placed perpendicular to the truss top chord to support the roofing.

Reaction:  Forces acting on a truss, through its support, that are equal but opposite to the sum of the dead and live loads.

Ridge:  Line formed by truss apexes.

Rise:  Vertical distance from bottommost part of the bottom chord to inside of the peak.

Scab:  Additional timber connected to a truss to effect a splice, extension or general reinforcement.

Shop Drawing:  Detailed drawings of a roof truss or roof framing showing critical dimensions such as span, overhang, cantilever, slope, etc.

Slope:  See Pitch.

Spacing:  Centerline distance between trusses - usually 24" O.C. (on center).

Span:  Horizontal distance between outside edges of the supports.

Splice Point:  (Top & Bottom chord splice).  The point at which two chord members are joined together to form a single member.   It may occur at a panel point or between panel points.

Square Cut:  End of top chord cut perpendicular to slope of the member.

Symmetrical Truss:  Truss with the same configuration of members and design loading occurring on each side of truss centerline.

Top Chord:  An inclined or horizontal member that establishes the upper edge of a truss - rafter in conventional frame.

Truss:  A pre-built component that functions as a structural support member.  A truss employs one or more triangles in its construction.

Truss-Clip:  Metal component designed to provide structural connection of trusses to wall plates to resist wind uplift forces.

Webs:  Members that join the top and bottom chords to form the triangular patterns that give the truss strength.