A making group
Made by Sawing
Cut from a log to a dimension, and sold by that dimension rather than by shape. One entry, and the material that changed how an ordinary wall is built more than anything else in this catalogue.
Selling a number
Every other group in this catalogue sells an object: a piece, a unit, a sheet. This one sells a cross section.
A mill saws thousands of identical pieces to a standard size and a builder buys them by the piece. The knowledge that used to live in the individual joint, cut by somebody who understood the whole frame, moves into a pattern instead: uprights at a regular spacing, doubled at openings, plates top and bottom, sheathing doing work that bracing used to do.
A wall becomes a repeated operation. That is the largest single change in how ordinary buildings were put up in this period, and it happened because a saw could be made to produce the same thing over and over.
The trap in the number
The name is not the measurement. A piece called two by four was sawn roughly to that size while green and then lost material to shrinkage and later to planing, and the name stayed while the wood shrank.
Anybody reading an old specification and expecting the stated figure to be the actual one will be wrong every time, and wrong in the same direction.
The one thing this group cannot show
Itself. Framing is the substance of most buildings here and it is behind a skin in nearly all of them, so a catalogue built on materials with a visible plane has to admit that this member is visible only when something is opened.
That limit is stated rather than worked around. This publication does not enter anybody's building, does not open anything, and treats what can be seen from a public sidewalk as the boundary of what it will describe.