>>6017777They open and close situationally. On the ground the L-Gaim uses them to jump, and in space they allow its thrusters to work.
There's actually a scene in some of the initial episodes where the MC, Daba, is fighting a gang of banditss with the L-Gaim, where they target and damage its opening leg binders to try and disable it.
If you ever give L-Gaim a try, it's nice show, but it suffers from mediocre subtitling. It's also a Tomino anime, IIRC his last work before Zeta and ZZ, and it shows. If you're a Nagano fan, you may recognize some designs that would change to become Mortar Headds.
https://www.youtube.com/watch?v=NjrEPdQgAMM 