Toshiba Satellite U840 Maintenance Manual page 134

Replacement Procedures
Screw Notation
To make maintenance of the computer easier, markings of the kinds of the screws including
the types and lengths are indicated on the computer body.
Format:
Screw shape + Screw length (mm)
Screw shape
B: Bind screw
F: Thin head screw
S: Super thin head screw
T: Tapping screw
U: Other screws (Unique screws: pan head, stud, etc.)
Example: B6 ... 6mm bind screw
Satellite U840 Maintenance Manual (960-Q08) 4-7