par·a·pet 
/ˈperəpət/ noun
plural par·a·pets /ˈperəpət/ noun [count] : a low wall at the edge of a platform, roof, or bridge
▪ The invaders fired arrows over the castle's parapet.
▪ The invaders fired arrows over the castle's parapet.
put/stick/raise your head above the parapet
Brit, informal : to do or say something you think is important even though it may have bad results
▪ I'll put my head above the parapet to defend him.
▪ I'll put my head above the parapet to defend him.
