Shimano GRX RX 815 Series Dealer's Manual page 52

INSTALLATION/REMOVAL
Installing the shifting switches
2.
Secure the shifting switch and adapter to the handlebar with a zip tie.
(1) Pass the zip tie through.
(2) Check that the zip tie has been passed through correctly, and tighten the zip tie.
(1)
Zip tie
Electric wire for shifting
switch
NOTICE
• When tightening the zip tie, take care not to also tighten the electric wire.
Failure to do so will cause operation failure.
Shifting switch
Adapter
52
(2)