3138: Dimensional Lumber Tape Measure

2025-09-08T06:54:03Z

2001:4C4E:1C07:C700:459E:9369:A847:EE25: 1 → sg

{{comic
| number = 3138
| date = September 5, 2025
| title = Dimensional Lumber Tape Measure
| image = dimensional_lumber_tape_measure_2x.png
| imagesize = 532x478px
| noexpand = true
| titletext = A person with two watches is never sure what time it is, especially if I got them one of the watches.
}}

==Explanation==
{{incomplete|This page was created by A LUMBERYARD PSYCHIATRIST. Don't remove this notice too soon.}}
A 2×4 is a type of dimensional lumber, meaning it is cut to a specified cross-section. In the case of a 2×4, despite implicitly specifying dimensions of 2 inches by 4 inches, its actual dimensions are 1.5 inches by 3.5 inches. The Dimensional Lumber Tape Measure "fixes" this inaccuracy by changing the length of some of its indicated inches so that a 2×4 is measured as 2 inches by 4 inches. On the dimensional tape the 1st, 2nd, and 8th division are made shorter than on the standard tape. So measurements that do not start at the beginning of the tape will give different values. Note that the comic states 7.125 inches as the width of a 1×8, when in reality the width is 7.25 inches.

As explained {{w|Lumber#Dimensional lumber|on Wikipedia}}, the nominal dimensions of a piece of dimensional lumber(US)/timber(UK) are those to which, in history, the wood was cut from green logs. Over time, the wood would shrink from loss of water. Consequently, a board cut to 2×4 inches would shrink to some fraction of those dimensions. The nominal dimensions also refer to the rough cut lumber - the final product is typically planed smooth, which further reduces its dimensions. The actual final dimensions would vary based on the type of wood, the amount of water lost and other such factors, with a greater or lesser amount of predictability. Over time, the actual dimensions of the wood became standardized at some regularly-achievable value less than the nominal dimensions. Different types of construction material sometimes use different measures, for instance, "1 inch" plywood is typically not 1 inch thick, but it is also not 3/4 inches thick (the thickness of a 1 inch board).

A person not familiar with this history may be puzzled at the disconnect between the nominal and actual dimensions of lumber/timber, perhaps to the point of thinking that some underhanded short-measure had gone on. To such persons, the comic's Dimensional Lumber Tape Measure makes sense, or at least addresses the disconnect. It would not, however, have any practical use, and attempts to employ it would likely lead to constructions going dangerously awry. Necessary lengths of timber, as well as other cuts that fine-tuned a supplied timber to fill a space, would be intrinsically inconsistent with the gaps they were intended to tightly fit within. At best, ''every single'' component of a construction would be measured and cut according to this particular measure and the resulting structure would be self-consistent but subtly undersized compared to the original plan.

Additionally, leaving it in someone else's toolbox without informing them would likely lead to them incorrectly measuring things, as the Dimensional Lumber Tape Measure appears visually similar to a standard tape measure and has similar enough units that it is plausible someone could use the Dimensional Lumber Tape Measure and assume it indicated full inches.

The title text is a play on the adage "A man with two watches is never sure what time it is". That adage is a rephrasing of {{w|Segal's law}}.

==Transcript==
{{incomplete transcript|So far, only the raw text was added. Needs description of the pictures and layout.}}

===Dimensional Lumber Tape Measure===

Dimensional lumber sizes are tricky. A “2×4” is actually 1½" by 3½", and a “1×8” is ¾" by 7⅛".

(A drawing of a rectangular wooden block labelled “2×4”, with notes indicating the length of the sides being 1½" and 3½".)

If you know someone into carpentry or woodworking, get them our ''dimensional lumber tape measure''.

(A drawing of two tape measures seen from the side. One is labeled <code>12'</code>, and the other is labeled <code>12'*</code>.)

(Two drawings of the tape measures’ tapes:)

Normal tape measure: (The measure is divided into inches evenly.)

Dimensional lumber tape measure: (The measure is divided unevenly, such that 1st and 2nd marked ‘inches’ are each equal to a ¾-inch but the 3rd to 7th marks each equate to a single 1 inch. The 8th mark is once again ¾-inch after the 7th.)

(Neither measure indicates the unit being used.)

'''Don’t tell them you got it'''—just leave it in their toolbox. They’ll appreciate the surprise when all their measurements work out!

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3138: Dimensional Lumber Tape Measure