English to Arabic Other General / Conversation / Greetings / Letters come down the lines

All the items end up here after they've been picked, and they are going to come down the lines and they'll be sorted into single pack and multiple pack.

We have some chutes. These are where our parcels are sorted and sent down the lines. So each conveyor belt is a different distribution center.

It is warehouse environment.

What could "down the lines" in these two different sentences?

Thanks in advance,