When writing clues, we often need to refer to a single letter as part of the wordplay. Unfortunately, English only has two one-letter words.

Cluing “I” is awkward for a two-person team, so we sometimes use the word right there in the clue:    IAGO I back the man who plays Othello (4)

The other one-letter word, “a,” can conceivably be clued as “article”, but “an article” would be weird. So we sometimes use it as is:    ACROSS  A hybrid alternative to down (6)

However, this in turn raises its own issues, bnecause there is a certain amount of looseness around the question of whether clues need articles for smooth surface or can use “headlinese.” So a solver can often be uncertain about whether “a” is contributing to the wordplay or merely the surface.

Another way to get single letters into a clue is by referring to their position in a word. “Fourth of July” is a classic way to indicate Y, and “fifth of whiskey” can be K.    BEETHOVEN’S THIRD  E is for “Eroica” (10,5)

Since there are only so many natural-sounding phrases in that format, the references are usually to first or last letters of words:    SPINAL  Originally, Sarah Palin edited a certain column (6)    BERET  Hat wearer finally cuts into vegetable (5)

That trick can be pretty transparent when it uses standbys like “originally” or “finally.” So we often strive to find indicators for first or last letters that sound more natural in context:    PRESIDIO  Fort Pulaski’s chief dies, or I fail (8)    IMAX  I can take in premiere of Moonraker in huge movie format (4)

Goofiness can also put solvers off the scent:    UNEARTHED  Vishnu’s foot—where the E might be dug up? (9)

One last technique for this post: a well-established cryptic convention is to refer to a letter by its shape. Here are a couple of examples using O:    AVOCADO  Fruit and eggs returned by rotter along with bagel (7)    GORILLA  Having eaten a donut, interrogate a thug (7)

In our next post, we’ll discuss abbreviations.

This week’s cluing challenge: HORSESHOE. To comment (and see other readers’ comments), please click on this post’s title and scroll to the bottom of the resulting screen.

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