I have placed a sign infront of bamboo by clicking on the bamboo. there is a gate below it. Even though the sign is placed with the bamboo, it will break when the gate is opened or broken.

However when the sign is placed on top of the gate by clicking on top of the gate. It will not break when the gate is open.
To summarize, the sign will break even if it does not rest or depend on the gate.
The picture attatched is of the arrangement in which it breaks.