Chuck is on the atmospheric pressure to fixed on the wall， so the wall more stringent requirements， must be absolutelysmooth and no leakage of the wall can be installed， so when you buy must pay attention to check whether their location to install to install suckers. If you want to install wall not installing sucker， sucker assisted version can be bought in this shop， the wall with chuck auxiliary plate， the sucker isarranged in the auxiliary plate， solved.