Switchable Handbrake Lever

Pull off the lower part of sleeve first, and then the upper part.

Twist and pull the rubber case toward the front. The case is only fixed by friction. This is the most difficult step of all.

Done.

Carefully insert a small flat-head screwdriver to remove the OEM button. The button is fixed by friction and two small latches.

You'll use this button in the new lever.

In order to cope with different car models and possible future changes by Toyota, the length of the extender can be adjusted by adding spacers. The overall length of "extender + spacers" affects how the locking mechanism works.

For GR-Yaris Gen-1, usually 1~2mm works.
For GR-Yaris Gen-2 or GR-Corolla, 4~6mm will be necessary.

Use more spacers if you feel the ratchets in both modes.
Use less spacers if the switch is stuck.

The spacer combination can be 1mm, 2mm, 3mm (2+1), 4mm, 5mm (4+1), 6mm (4+2), 7mm (4+2+1), 8mm (4+2+1+1).

Put the button extender and the switch ring on.

Clamp the left and right halves of lever on and tighten the 5 hex bolts. Be careful not to damage the threads and the plastic lever case.

0.5 N.m (0.37 lb-ft) torque would be enough.
Loctite 243 thread locker or equivalent is recommend.

Hook the sleeve onto the upper part first, and then the lower part.