As Airdale stated, that is the way to adjust the free play in the steering box. Years ago I read that you need to have a friend turn the steering wheel as you remove the freeplay at the box, otherwise you can possibly damage the box. I believe that it can bind, if you don't crank the wheel while it is adjusted.
Also, check the steering coupler. Unbolt it and inspect it for tears. I recently had one that was literally ripped throughout, but it was not visible with it installed.
A panhard bar will also help a lot.