Siemens Simatic S7-1500 - Page 30

Hardware section
2.3 Wiring
S7-1500
30 Getting Started, 05/2014, A5E03981761-AC
3. Move the front connector from the pre-wiring position to its final position. By doing this,
you create an electrical connection between the front connector and the module.
4.
Tip:
Pre-wired front connectors, e.g. for replacing modules, can be inserted directly.
Result
The front connectors are now wired.