Riddles to the left of me, riddles to the right of me, stuck in the riddle with you!

 

In Wonder I’m crafted by children at play.

United I stand, divided I fall.

Growing stringer by night and weaker by day;

My death knell is heard in a red robin’s call.

 

If you think you know the answer posted it in the comment section below. I will confirm the correct answer once it is posted! Good Luck