I rarely do barbell squats, I put my feet in front of me and go as deep as possible while putting all the emphasis on my quads. for hams I do the same thin with a wide stance and toes pointed out. I strongly disagree that free weight squats build more muscle overall. actually, that's wrong, they build more OVERALL muscle because it works everything, however, when I wanna work my legs, I concentrate on my legs, not everybody part at the same time.