SIM800L SMS RELAY v1.0 * Arduino Hardware (Author): Nano V3 (ATmega328 ... The SIM card must be inserted into the slot with its contacts facing the circuit board and the notched end sticking out.

There are 12 connections in total (6×2 rows) on the SIM800L module and, surprisingly, one row contains all of the connections required to interface with a microcontroller like the venerable Arduino ..