##Block arrows
##block arrow
##Use the 'block' keyword to convert an arrow to a block arrow. Some arrowhead variants can only be applied to arrows or block arrows, some for both.
C: Client;
R1: Router;
R2: Router;
S: Server;

->C: Hit;
C<->S: Query/Response\n\-(normal);
block C<->S: Query/Response\n\-(block);
