This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
All partition walls are finished at the top and bottom by horizontal pieces, called, respectively, the "cap" and the "sole." The sole rests directly on the rough flooring whenever there is no partition under the one which is being built; but if there is a partition in the story below, the cap of the lower partition is used as the sole for the one above. The sole is made wider than the stud-ing forming the partition wall, so that it projects somewhat on each side and gives a nailing surface for the plasterer's grounds and for the inside finish. It is usually made about 2 inches thick and 5 1/2 inches wide, when the partition is composed of 4-inch studding, and this leaves a nailing surface of 3/4 of an inch on each side. The sole is shown at B in Fig. 124. The cap is usually made the same width as the studding, and 2 inches thick, so that a 2 X 4-inch piece may be used in most cases; but if the partition is called upon to support the floor beams of the floor above, the cap may have to be made 3 or even 4 inches thick, and some architects favor the use of hard wood such as Georgia pine for the partition caps. The cap is shown at A, Fig. 125.
Fig. 124. Partition Framing Showing Sole.
Fig. 125. Partition Framing Showing Cap.