Maxview Roam Teltonika Router
The SIM slot is located underneath the mobile strength indicator LED's, diagram below:
More information on how to install a SIM on a Teltonika router
Huawei E5577
The SIM slot is located underneath the battery. To access, pop off the back cover and remove the battery.
More information on how to install a SIM on a Huawei 5577
Huawei B315
The SIM slot is located on the side of the router.
For more information on how to install a SIM on a Huawei B315