Unlocking History Number (UH#)

UH6203

Original

Letterlocking Categories and Formats Chart, updated 2023.

Model and research notes

MIT Libraries, Unlocking History Research Group archive, MC0760, Box 01.

Letterlocking Unique Video Number(s) (LUV #s) & Instructional video(s) URL

LUV### [link to video URL here]

Instructional video info transcription

Forthcoming

Letterlocking category Number (LC #)

All

Letterlocking format Number (LF #)

All

Security score

Zero, Low, or High

Assessment of Confidence in assigning LC#

NA

Substrate

NA

Dimensions

NA

Manifestation

NA

Distinctive letterlocking style(s)

NA

Locking Mechanism

Closure flap, Lock, Hybrid-lock, and Tuck

Security enhancements

NA       

Letterlocking category formula (shorthand)

ALL

LC1 

Fold

(F)

LC2 

Fold + Tuck 

(F + T) 

LC3 

Fold + Slit/Hole 

(F + S/H)

LC4 

Fold + Tuck + Slit/Hole 

(F + T + S/H)

LC5 

Fold + Adhere

(F + A)

LC6 

Fold + Tuck + Adhere 

(F + T + A)

LC7 

Fold + Slit/Hole + Adhere 

(F + S/H + A)

LC8 

Fold + Tuck + Slit/Hole + Adhere 

(F + T + S/H + A)

LC9 

Fold + Lock-O 

(F + LO)

LC10 

Fold + Tuck+ Lock-O  

(F + T + LO)

LC11 

Fold + Slit/Hole + Lock-O 

(F + S/H + LO)

LC12 

Fold + Tuck + Slit/Hole + Lock-O  

(F + T + S/H + LO)

LC13 

Fold + Adhere + Lock-O

(F + A + LO)

LC14 

Fold + Tuck + Adhere + Lock-O  

(F + T + A + LO)

LC15 

Fold + Slit/Hole + Adhere + Lock-O 

(F + S/H + A + LO)

LC16 

Fold + Tuck + Slit/Hole + Adhere + Lock-O 

(F + T + S/H + A + LO)

LC17 

Fold + Lock-SU 

(F + LSU)

LC18

Fold + Tuck + Lock-SU

(F + T + LSU)

LC19 

Fold + Slit/Hole + Lock-SU 

(F + S/H + LSU)

LC20 

Fold + Tuck + Slit/Hole + Lock-SU 

(F + T + S/H + LSU)

LC21 

Fold + Adhere + Lock-SU

(F + A + LSU)

LC22 

Fold + Tuck + Adhere + Lock-SU  

(F + T + A + LSU)

LC23 

Fold + Slit/Hole + Adhere + Lock-SU 

(F + S/H + A + LSU)

LC24

Fold + Tuck + Slit/Hole + Adhere + Lock-SA 

(F + T + S/H + A + LSU)

LC25 

Fold + Lock-SA 

(F + LSA)

LC26 

Fold + Tuck + Lock-SA  

(F + T + LSA)

LC27 

Fold + Slit/Hole + Lock-SA 

(F + S/H + LSA)

LC28 

Fold + Tuck + Slit/Hole + Lock-SA 

(F + T + S/H + LSA)

LC29 

Fold + Adhere + Lock-SA

(F + A + LSA)

LC30 

Fold + Tuck + Adhere + Lock-SA 

(F + T + A + LSA)

LC31 

Fold + Slit/Hole + Adhere + Lock-SA 

(F + S/H + A + LSA)

LC32 

Fold + Tuck + Slit/Hole +Adhere + Lock-SA  

(F + T + S/H + A + LSA)

LC33 

F + Lock-O + Lock-SU 

(F + LO + LSU)

LC34

Fold + Tuck + Lock-O + Lock-SU  

(F + T + LO + LSU)

LC35 

Fold + Slit/Hole + Lock-O + Lock-SU 

(F + S/H + LO + LSU)

LC36 

Fold + Tuck +Slit/Hole + Lock-O + Lock-SU

(F + T + S/H + LO + LSU)

LC37 

Fold + Adhere + Lock-O + Lock-SU

(F + A + LO + LSU)

LC38 

Fold + Tuck+ Adhere + Lock-O + Lock-SU 

(F + T + A + LO + LSU)

LC39 

Fold + Slit/Hole + Adhere + Lock-O + Lock-SU 

(F + S/H + A + LO + LSU)

LC40 

Fold + Tuck + Slit/Hole 

(F + T + S/H + A + LO + LSU)

LC41 

F + Lock-O + Lock-SA  

(F + LO + LSA)

LC42 

Fold + Tuck + Lock-O + Lock-SA 

(F + T + LO + LSA)

LC43 

Fold + Slit/Hole + Lock-O + Lock-SA

(F + S/H + LO + LSA)

LC44

Fold + Tuck + Slit/Hole + Lock-O + Lock-SA 

(F + T + S/H + LO + LSA)

LC45 

Fold + Adhere + Lock-O + Lock-SA

(F + A + LO + LSA)

LC46 

Fold + Tuck + Adhere + Lock-O + Lock-SA 

(F + T + A + LO + LSA)

LC47 

Fold + Slit/Hole + Adhere + Lock-O + Lock-SA  

(F + S/H + A + LO + LSA)

LC48 

Fold + Tuck + Slit/Hole + Adhere + Lock-O + Lock-SA 

(F + T + S/H + A + LO + LSA)

LC49 

F + Lock-SU + Lock-SA 

(F + LSU + LSA)

LC50 

Fold + Tuck + Lock-SU + Lock-SA  

(F + T + LSU  + LSA)

LC51 

Fold + Slit/Hole + Lock-SU + Lock-SA  

(F + S/H + LSU  + LSA)

LC52 

Fold + Tuck + Slit/Hole + Lock-SU + Lock-SA  

(F + T + S/H + LSU  + LSA)

LC53 

Fold + Adhere + Lock-SU + Lock-SA

(F + A + LSU + LSA)

LC54 

Fold + Tuck + Adhere + Lock-SU + Lock-SA 

(F + T + A + LSU + LSA)

LC55 

Fold + Slit/Hole + Adhere + Lock-SU + Lock-SA 

(F + S/H + A + LSU  + LSA)

LC56

Fold + Tuck + Slit/Hole + Adhere + Lock-SU + Lock-SA  

(F + T + S/H + A + LSU + LSA)

LC 57

F + Lock-O + Lock-SU + Lock-SA

(F + LO + LSU + LSA)

LC58 

Fold + Tuck + Lock-O + Lock-SU + Lock-SA 

(F + T + LO + LSU  + LSA)

LC59 

Fold + Slit/Hole + Lock-O + Lock-SU + Lock-SA

(F + S/H + LO + LSU  + LSA)

LC60 

Fold + Tuck+ Slit/Hole + Lock-O + Lock-SU + Lock-SA  

(F + T + S/H + LO + LSU  + LSA)

LC61 

Fold + Adhere + Lock-O + Lock-SU + Lock-SA

(F + A + LO + LSU  + LSA)

LC62 

Fold + Tuck + Adhere + Lock-O + Lock-SU + Lock-SA 

(F + T + A + LO + LSU  + LSA)

LC63

Fold + Slit/Hole + Adhere + Lock-O + Lock-SU + Lock-SA 

(F + S/H + A + LO + LSU  + LSA)

LC64 

Fold + Tuck + Slit/Hole + Adhere + Lock-O + Lock-SU + Lock-SA 

(F + T + S/H + A + LO + LSU + LSA)

Letterlocking manipulation sequence (shorthand)

NA

Locking instructions

NA

Images 

Forthcoming

Images: View: address side; reverse side

Images: Download: address side; reverse side

Foldable(s)

NA

Step-by-steps 

NA

Substrate map

NA

Virtual unfolding results

NA

Manipulations

NA

Damage

NA

Features

NA

Article(s)

2021. Unlocking history through automated virtual unfolding of sealed documents imaged by X-ray microtomography 

Book 

Jana Dambrogio, Daniel Starza Smith, and the Unlocking History Research Group. Letterlocking, The Hidden History of the Letter. Cambridge and London: MIT Press, 2025.

Citation for the letter(s)

Letterlocking Categories and Formats Chart, updated 2023.MIT Libraries, Unlocking History Research Group archive, MC0760, Box 01.