Will i be able to remove these?

Hello, I’m trying to make a player model by rigging the skeleton on a model and I’m kinda confused with the reference valve biped skeleton on Blender.

What are those short grey solid lines and what do they do?
Will I be able to remove them with no problems done to the player models?

Screenshot :

http://puu.sh/kns5h/fcbdaac1c7.jpg

they’re joints idk why you would want ot get rid of them but ok