For a long stretch of history shoes were made without a left or a right

A shoe is made on a shape, not on a foot

Every shoe is built around a last, a solid form approximating a foot, over which the upper is stretched and to which the sole is attached. The last determines the interior shape, and it’s the most important object in shoemaking, because it and not the foot is what the shoe is actually copied from.

Making lasts by hand is skilled, slow work, and making them in mirrored pairs doubles the effort while halving the flexibility of the stock. A symmetrical last, by contrast, produces a shoe that will serve either foot, which simplifies making, storing and selling considerably.

Those pressures are why straights — shoes made on symmetrical lasts and worn on either foot — were common in Europe for a long period, particularly from around the seventeenth century into the nineteenth. It was not universal and it was not an unbroken rule, and earlier footwear in various traditions was clearly shaped for each foot.

Wearing a straight was not as absurd as it sounds

The materials help to explain it. A leather upper worn regularly moulds to the foot, so a straight shoe becomes a left or a right in use, and wearers were commonly advised to swap them between feet to even out the wear.

Soles were also generally flat and the fit was looser than modern footwear, since foot-shaped support was not something anybody expected from a shoe. Comfort standards were different, and comfort in general was a lower priority in dress than it has since become.

It is still fair to say straights fitted worse. Contemporary complaints exist, and shaped footwear was made for those who could pay for it, which is a decent indication that the symmetrical version was an economy rather than a preference. The people who suffered most were those given footwear rather than fitted for it, which in practice meant soldiers, servants, prisoners and the enslaved, since a shoe issued from a barrel of identical shoes is a shoe that fits nobody in particular.

Military supply and machinery brought the pairs back

Large-scale supply of footwear to armies concentrated attention on fit, because soldiers who cannot march are a serious problem, and standardised production for such contracts is one of the settings in which shaped lasts and graded sizes advanced through the nineteenth century.

Machinery did the rest. The mechanisation of last-turning, and then of the operations of shoemaking themselves, made it feasible to hold a large stock of lasts in mirrored pairs and across a range of sizes and widths, since the cost of each additional form fell sharply.

By the later nineteenth century mass-produced footwear in lefts and rights was ordinary, and the straight had become an oddity. The change is a fair illustration of a general pattern: an improvement in fit arrived when production made it cheap, rather than when the need for it was first noticed.

Sizing systems grew from the same soil

Standardised sizes require standardised lasts, so the arrival of graded footwear sizing follows the same industrial curve. The systems that resulted were regional, and they were built on different base units and different increments, which is why converting between them today is approximate rather than exact.

Width fittings were part of the same development and were far more widely offered in some markets than others. Where they persist, they are the remnant of a period when footwear was sold as a fitted product rather than a boxed one.

None of these systems describes a foot completely, since a foot has girth, instep height, arch length and heel width as well as overall length. The last still carries all of that information, and the size printed on the box carries one number of it.

What survives of the older approach

Bespoke shoemaking still begins with a last made or adjusted for one person, and that is precisely the part that justifies the price. Everything else in the process is craft that can be bought elsewhere; the individual last is what cannot.

Some traditional footwear remains genuinely symmetrical or nearly so, and moccasin-type constructions and certain sandals sit closer to the older logic, relying on soft material moulding to the foot rather than on a shaped form.

And the practice of rotating footwear between days, which is now recommended for moisture reasons, has a distant relative in the old instruction to swap straights between feet. The reasoning has changed completely. The habit turns out to have been sound for a different reason all along.