Window Balance to hold window up

Hey there. If the windows won't stay open, it's likely due to the window balances failing. They're spring-loaded mechanisms that regulate the movement of the window sash. There's many different kinds, which you can review here. See which you have, then send us the proper photos and measurements, and we'll do our best to narrow down what you need to get these windows working. 

Guide: Everything you need to know about window balances