Assembling Monarco HAT and Raspberry Pi 4B
Step 1 - Raspberry Pi

Use metal spacers to attach the Raspberry Pi to the bottom part of the aluminium case and stick the thermal conductive pad.
Step 2 - Heat Sink

Screw the heat sink to the side panel.
Step 3 - Side Panels

Mount the side panels and tighten the screws.
Step 4 - Isolation Pad

Stick an isolation pad on the battery from below Monarco HAT.
Step 5 - Monarco HAT

Attach the Monarco HAT on top of the Raspberry Pi and use screws to fasten it.
Step 6 - Closing the Case

Mount the cover and tighten the screws.
Step 7 - Connector and micro SD card

Plug in the connector and micro SD card. Make sure that the locking levers are in the middle position.
Step 8 - Mounting holders
Insert two plastic holders according to your preferences. The metal case allows for both horizontal and vertical mounting.
Step 9 - DIN rail mounting

The aluminium case allows vertical mounting...

... as well as horizontal mounting.