Tracing plane line

[8cork]

I've been working for the past few days on tracing the straight plane line using a golf club box as a guide. I can hit shots all day with my right arm only, never touching the box. But, for some reason, when I add my left arm and hit shots I graze the top of the box about a foot and a half back in my backswing, and occasionally whack it on the downswing. I am trying to concentrate on right arm pickup. Any tips or suggestions?

[EdZ]

Check your shoulder alignment. It is likely that you have worked into a slightly open position (the natural move when hitting right hand only).