Rafters of uniform size regularly spaced along the length of a roof, or intermediate between principals; a pair of common rafters is a couple.
see also Couple
A) Box-frame construction C) Closed truss
a) Sill beam b) Post c) Stud d) Transverse beam e) Common rafter f) Couple g) Principal h*) Collar i) Queen strut j*) Tiebeam k) Axial beam
A) Base cruck F) Two-tier cruck
f*) Plate i) Upper tiebeam j) Lower tiebeam k) Common rafter m) Joggled halving n) Barefaced dovetail p) Spur