Lenovo T420 - Manual (Page 90)

Step Screw (quantity) Color Torque
3 M2 × 3 mm, wafer-head, nylon-coated (1) Black 0.181 Nm
(1.85 kgfcm)
4 Shoulder screw (2) Silver 0.181 Nm
(1.85 kgfcm)
84 ThinkPad T420 and T420i Hardware Maintenance Manual