In building cutting two 1metre long pieces of timber will not give a 2 metre piece unless some sort of fixing is used (for non structural uses only),

I understand mathematics abstracts to a desired unit of a dimension, in the timber case,length and it compares length units. The reason for measuring
is for use and use depends on whole planks.

I propose using the + symbol attached to answer to indicate the length is a group of timbers rather than one single uniform entity. Of course, there can be work done to convert +2 or 2+ to 2, then all good with restrictions. A negative grouping is already signed because naturally nothing is self aggregating and is whole by its very presence against not negative. If units use requires, certain negative units might need something like -2-.

Summing up, at least with 10$, you know what you are going to get. +10$ not so much.

If it's any consolation, the Venn diagram for this idea has two domains, one of which contains [wjt] as its sole member, and the other which contains "everyone else".

It must be admitted that the introduction of the concept of the "negative plank" is uniquely innovative. For those presented with the problem of a plank which is slightly too long for the assigned task, rather than cutting off a portion (which is wasteful), attaching an appropriate length of negative plank is much more elegant.

It would also grealy simplify transport of long lengths of material. If, for example, a long length of pipe had an equal length of negative pipe attached prior to shipping, the space occupied would be proportionately reduced, and smaller vehicles could be used. After delivery, the negative pipe would be detached, and each pair of negative pipes combined to give an additional length of normal pipe.

It's just astonishing that this has never previously been tried.

No, no, no, NO. Sheesh, how can you be so ignorant? You can buy one length of positive (normal) pipe for the usual price, or two lengths of negative pipe for twice that price.

Where you save is on the shipping. You buy two positive pieces and two negative pieces The negative pieces are each joined to a positive piece for transport, thus occupying zero length (although the diameter is unchanged). On delivery you unpack the zero length pipe, separate it into positive and negative portions, and join the two negative lengths together to make a double positive length. You then have the equivalent of four lengths of pipe.

Actually, this idea made perfect sense to me. I'll go back to bed 'till I feel
better.

(Not saying I agreed with it - if my shipment ended up containing a +1
gallon glass jug of maple syrup, when it was only intended to be 1, I'd
disagree with the "+" nomenclature.)