Answer:
Both of those are about feelings. But different parts of feelings. A fence is a way to block or stop though feelings from either coming or to build up a fence to hide those feelings. A mending wall is to help heal those feelings and make it so it is like you are helping your feelings. The authors tone is he is either trying to block his feeling and hide them"for the fence". And heal or mend his feelings and take down that wall"for mending wall".
Step-by-step explanation:
Hope this helps!!