Board Thread:Questions and Answers/@comment-30807378-20161221020555/@comment-26828130-20161221142614

A little correction to Marvel's reply:

Rewarded items, that are required by contracts/achievements, can't be sold, and don't take storage space Also items bought with gems don't take storage space (but they can be sold!)

You recognise these items by the green amount numbers (upper-right corner of the items) Normal items, and rewarded items that aren't required by contracts/achievements have the amount numbers in black, those take storage space, and if you don't want to sell them you can keep them behind your biggest (unused) loco (preferably a steamer) in depot to save storage space