In the National Puzzlers League, flats are wordplay puzzles (mostly) based on a relationship between two or more words or phrases, for instance, (sword, word) is a beheadment. A flat is accompanied by a verse into which the answer words fit, but those words are replaced by other words, called cue words, usually written in all caps. The cue words should indicate the relationship of the words, either by order or example. In addition, an enumeration of the length of one or all of the answer words is given; this may be accompanied by additional tagging if the words are capitalized or not in a common abridged dictionary (the Merriam-Webster dictionaries are the usual sources).

Example flat:

BEHEADMENT (5)

You can't use a BREAD
To cut off the head
Of a READ.

The cue words BREAD and READ represent the answer words "sword" and "word". The (5) indicates the length of the first answer word; the length of the second answer is not given because in a beheadment it is constrained to be 4 letters.