A penknife was an essential accessory for a scribe, both to cut a feather into a quill pen and for erasing mistakes by scraping the surface of the parchment. Penknifes generally had quite short blades which were narrow and capable of being sharpend to a fine edge. The blade was curved on one side and straight on the other to facilitate shaping the pen. The handle, made of metal, horn, ivory, amber or other materials was often rectangular or octagonal to help give the user a firm grip. Many penknifes had a small point or peg at the end of the handle. This was used to widen the slit in the pen's nib. Martin Billingsley, an English writing master of 1619, describing the use of a penknife, wrote: '....take the end of your knife if it have a pegg, or else another quill, and make a slit up suddenly, even in the cut you gave before.'

Preparing a feather to make a quill pen involved tempering the quill with hot sand then cutting the feather away from the stalk especially if ‘horish or skirtie’ (dirty or filthy). Instructions from a writing manual of 1571 told the writer to scrape the feather with ‘the backe or heele of your penknife’ and then sharpen the tip and make a slit for the ink to flow. Quill pens required constant sharpening or ‘mending’ during use.