The four post is really stable even without being bolted to the floor. It came with a caster kit that could be used to move the lift around the garage. My garage isn't really big enough for that. I have considered bolting to to the floor anyway, just for the peace of mind.ITLRUN, I am leaning towards a four post than a two post lift. I see yours is not bolted to the concrete which I will not do either. When your car is up in the air on it, is it pretty stable? I've never seen a four post in person. It only makes sense that there has to be a tight fitting guide on the four corners to keep that from wobbling around with weight on it.