Master key chart

Canton Hyland Hardware & Building Material Co., Ltd. · cantonlock.com/news/master-key-chart-how-to-read-and-draw-one/

One row per key, one column per door. Write the door numbers from the drawings across the top.
Mark a cross where the key opens the door. Read a row to see everything one key opens; read a column to see every key that opens one door.
Symbols follow the DHI convention: two levels AA and 1AA, 2AA; three levels A, AA, AA1; four levels GGM over A and B. A cylinder opened by more than one branch is cross-keyed: write X before its symbol and name every key in the notes.
Count each row (doors per key) and each column (keys per door) before the chart is approved. A column with crosses from two masters is a cross-keyed cylinder.
Printing: use landscape. “Save as PDF” in your browser gives the same sheet to send by email.

Project / building
Keyway (one for the whole system)
Levels in use
Revision and date

Key symbol	Level	Held by	Copies																	Doors




















Keys that open this door

Notes (cross-keyed cylinders, doors kept off a master, keyed-alike sets):

Worked example — a two-floor clinic, three levels

Grand master A; masters AA (ground floor), AB (first floor), AC (service); change keys under each. Door 202 has no change key, so its cylinder carries the master's symbol, AB.

Key symbol	Level	Held by	Copies	101 Reception	102 Consulting 1	103 Consulting 2	201 Office	202 Records	203 Staff room	001 Plant room	002 Cleaner's store	Doors
A	Grand master	Clinic owner	2	×	×	×	×	×	×	×	×	8
AA	Master	Practice manager	1	×	×	×						3
AB	Master	Office manager	1				×	×	×			3
AC	Master	Maintenance contractor	1							×	×	2
AA1	Change key	Reception staff	2	×								1
AA2	Change key	Doctor, room 1	2		×							1
AA3	Change key	Doctor, room 2	2			×						1
AB1	Change key	Office staff	2				×					1
AB2	Change key	All staff	4						×			1
AC1	Change key	Maintenance contractor	1							×		1
AC2	Change key	Cleaning staff	2								×	1
Keys that open this door				3	3	3	3	2	3	3	3

Lose AB and the chart answers what to recore: read its row, doors 201, 202 and 203. Lose A and every cylinder in the system is exposed, which is why the grand master has the fewest copies.