The only time most modern people have any contact with a straight pin is trying to wrestle one free from the packaging of a new dress shirt. But to an 18th c. lady, the straight pin wasn't a nuisance. It was a necessity.
Not only were pins used in sewing and mending, but they were also employed to fasten clothes together: a gentleman's neckcloth, the front bodice of a lady's gown (as shown in the detail, below right, of the gown seen here earlier this week), even a baby's diapers. Pins were most commonly purchased in a milliner's shop (see Loretta's blog.)
The picture, above left, shows a selection of replica 18th c. pins: the smaller ones are for sewing, while the longer ones are "dressing pins."
The dressing pins have the larger heads, formedas the wire is twisted around the unsharpened end. The gold-toned pins are made of brass, with the advantage that they did not rust; the silver-toned ones are steel, which holds a sharper point than the brass, but rusts.
Also in the above photo is a reproduction of an original paper packet that would have held two or three dozen pins. Henry Halles was one of the largest pin manufacturers in 18th c. England; the industry was centered in the London neighborhood of Whitechapel.
Pins were so essential to the 18th c. lady that the British trade embargoes against American colonists during the Revolution made their price skyrocket in Boston and other colonial cities. Ladies could live without tea. Pins were quite another matter. Abigail Adams famously wrote from Massachusetts to her husband John in London in 1775, begging him to "purchase me a bundle of pins & put them in your trunk for me. The cry for pins [in Boston] is so great, that what I used to buy for seven shillings and sixpence, are now twenty shillings, and not to be had for that."
Many thanks to tailor Mark Hutter of Colonial Williamsburg for both his pins, and his considerable knowledge.