How would I create a retractable lightsaber?

So I’m making a star wars game (probably not going to release it unless I get premmision by Disney which is very unlikely) where you can play as darth vader. I have made a lightsaber model (split into 2 parts: the saber itself and the hold) and I want to know how I would make it retract and extend when I press a key.

It just so happens, that I made a lightsaber type thing in UE4 a little while ago. I’ve made the project available for download to anyone. It uses engine version 4.10, so you might need that one to work if it doesn’t update correctly to a newer version by itself. You can download it and check out all the blueprints and stuff.

Thank you so much. Been looking for a week now.