Letter in runes
Letter in Socrates' name
Letter in some fraternity names
Letter in the Bible
Letter in the classical spelling of "Athena"
Letter in the Daily Mirror
Letter in the Globe and Mail
Letter in the Greek or NATO alphabet
Letter in the London Times
Letter in the NATO alphabet
Letter in the W.W. II phonetic alphabet
Letter insert, briefly
Letter insert: Abbr.
LETTER intended for extensive circulation
Letter jacket wearer
Letter letters
Letter line
Letter lines
Letter lineup
Letter made with two fingers
Letter man
Letter man of TV
Letter man's house
letter New Testament book
LETTER not a capital
Letter number
Letter O?
Letter of a chapter?
Letter of approval?: Abbr.
letter of challenge
letter of credit
Letter of indictment?
letter of recommendation
letter of recommendation from a previous employer
Letter of the alphabet
letter of the law
Letter of the law?
Letter often accompanying 55-Across
Letter often written by Rhodes scholars?
letter Old English
Letter on a blue skintight suit
Letter on a college sweatshirt
Letter on a dreidel
Letter on a frat house
Letter on a frat house, perhaps
Letter on a house used by 4-Across
Letter on a key
Letter on a marker
Letter on a screen
Letter on a sorority house
Letter on a sweater
Letter on a transcript
Letter on an honor society key
Letter on fraternity row
Letter on Kal-El's chest
Letter on Kal-El's costume
Letter on some campus sweatshirts
Letter on some college jackets
Letter on some euros
Letter on some gold keys
Letter on some keys
Letter on Superman's chest
Letter on the AutoSum button in Excel
letter opener
Letter opener, at times
Letter opener, maybe
Letter opener, of a sort
Letter opener, sometimes
Letter opener: Abbr.
Letter opener?
Letter opener's creation
Letter opener's cut
Letter openers
Letter opening
Letter opening?
Letter opposite 16-Across
Letter or number
letter or symbol representing a sound
Letter pair in 'pummel'
Letter paper?
Letter part
Letter preceding bravo
Letter preceding iota
LETTER presenting more than one sound (philol.)
Letter prevalent in Mississippi?
Letter producer
Letter pronounced while breathing out
Letter puzzle
Letter receiver
Letter recipient
Letter representing sound
LETTER representing sound that is part vowel and partly consonant
Letter resembling a pitchfork
Letter resembling a trident
Letter resembling an H
Letter resembling an inverted "V"
Letter resembling an ox's head
Letter resembling an X
Letter resembling H
Letter routing abbr.
Letter run
Letter salutation
Letter sealer
Letter seen in a Christogram
Letter seen on frat row
Letter seen twice in Philadelphia
Letter send-off
Letter sender
Letter sender from afar
Letter sent through cyberspace
Letter sequence
Letter sequence that symbolizes easiness
Letter series
Letter shaped like a horseshoe
Letter shaped like a P
Letter shaped like an upside-down U
letter shaped ski lift
letter shaped strut hyph
Letter shuffle
Letter shuffles
Letter sign-off
Letter signoff
Letter similar to a German Eszett
Letter sound
Letter spelled by inserting a letter into another letter
Letter start
Letter starter
Letter starter of yore
Letter stick-on
Letter string
Letter stroke
Letter strokes
letter style
Letter successor, to a large degree
letter such as m or n
letter such as n or m
letter Sweater
Letter switched to ess in this puzzle's theme
Letter taker
Letter taker, for short
Letter takers, for short
Letter than rhymes with the ones just before and after it
Letter that appears at least once in every single answer in this puzzle
Letter that appears twice in the Schrödinger equation
Letter that bends 90 degrees
Letter that can have a cedilla in French
Letter that comes before upsilon
Letter that doesn't need a stamp
Letter that doesn't need an envelope or stamp
Letter that follows epsilon
Letter that follows pi
Letter that forms a right angle
Letter that hints at how 18 answers in this puzzle should be filled in
Letter that looks like a pitchfork
letter that looks like a slingshot 2wds
Letter that may be used by 61-Down
Letter that might go through a filter
Letter that might include an emoticon
Letter that opens with a click
Letter that requires clicking, not licking
Letter that requires no postage
Letter that resembles the "y" of Disney's signature
Letter that rhymes with "theta"
Letter that rhymes with 34-Across and 21-Down
Letter that rhymes with its preceding and following letter
Letter that rhymes with its two successors
Letter that rhymes with three other letters
Letter that rhymes with three others
Letter that some feel should have its own day, rather than pi having Pi Day
Letter that sounds like a question
Letter that sounds like a swath of seats
Letter that sounds like an expression of relief
Letter that, surprisingly, is not the end of the Greek alphabet
Letter that's also a name
Letter that's an anagram of 111-Down
Letter that's an anagram of 16-Across
Letter that's not really at the end of the Greek alphabet
Letter that's opened with a double-click
Letter thought to resemble a skull
Letter through a filter
Letter to a Viking?
Letter to cross
Letter to Liverpudlians
Letter to Odin?
Letter to Santa
Letter to the ___
Letter to the editor that might be received immediately
Letter to the editor, often
Letter to Yanni?
letter toppers
Letter train
Letter trio
Letter two after tau
Letter two before iota
Letter two before tau
Letter upon which this puzzle's theme is built
Letter used as a density symbol
Letter used in Old English and Icelandic
Letter used to represent resistance
letter v
Letter vendor?
Letter voiced by a Greek giant?
Letter wearer: Abbr.
Letter wearers, e.g.
Letter widths
Letter with a 90-degree bend
Letter with a double curve
Letter with a double twist
Letter with a limited amount of space
Letter with a right angle
Letter with a silent letter
LETTER with cost of answer free to sender
Letter with curves
Letter with no curves
Letter with the largest section in a dictionary
letter wrapper
Letter writer, of a sort
Letter writer?
Letter writer's afterthoughts
Letter writer's aid
Letter writer's embellishment
Letter writer's signoff
Letter writing and sentence diagramming, it's said
Letter writing, for example
Letter writing, it's said
Letter writing, some say
Letter written as a straight vertical line
Letter X?
Letter Y sporter
Letter you can read without the light on
Letter you don't pronounce in "jeopardy" and "leopard"
letter Zola Author
Letter-bottom abbr.
Letter-bottom letters
Letter-box inscription
Letter-cartification words
Letter-closing word
Letter-closing words
Letter-drawing guide
Letter-ending abbr.
Letter-ending word
Letter-erasing key
Letter-extending abbr.
Letter-getter, for short
Letter-getting opportunities
Letter-handling org.
Letter-named thoroughfares in Bklyn.
Letter-opening word
Letter-perfect
Letter-perfect contest?