What is Put in ?
Put in is (verb) 1. to place something inside I forgot to put in my pyjamas when I packed the case. 2. to fix something such as a system or a large piece of equipment in place so that it can be used The first thing we have to do with the cottage is to put in central heating. 3. to do work She put in three hours’ overtime work yesterday evening. 4. to put in for to apply for She put in for a job in the accounts department. He has put in for a grant to study in Italy.
source: Easier English, Student Dictionary Upper Intermediate Level