Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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Unified Thread Identification





1. Bolts:
A circular recess is stamped in the upper surface of the bolt head.
2. Nuts:
A continuous line of circles is indented on one of the flats of the hexagon, parallel to the axis of the nut.
3. Studs, Brake Rods, etc.:
The component is reduced to the core diameter for a short length at its extremity.