how do i teach my son [age 8]

Question
when does he block a gap man or a linebacker? he plays left gaurd.  

Answer
Dear Justin,
The basic rules for blocking are as follow; the man who is head-up on you, inside gap, outside gap, and linebacker. You always want to block the man who is head-up on you first. If no one is head-up, you look for the man in your inside gap. If no one is in your inside gap, you look for man who is in the outside gap. And if no one is in the outside gap, you look for the linebacker nearest you.

You have to understand that not all coachs use the same rules, so you need to check with your son's coach to be sure.

Some coachs like to control play-side gaps only. For example, if the play is going to the right, they have everybody block to the rightside gap only. If the play is going to the left, they block leftside gap only. And if nobody is in your gap, they want you to go after the linebacker.

So be sure to check with your son's coach first, to make sure you are on the same page.
Your friend, Coach Louis