Sindoh M611 - Manual (Page 208)

Maintenance and Troubleshoot
5-
8
5 Follow below steps.
A. Hold the handle with your palm facing upward.
B. Align the front hooks (arrow sticker) of the cartridge to the guides (arrow sticker) of the device.
C. Push the cartridge into the device until you hear a click.
6 Close the front cover.