Chuck is on the atmospheric pressure to fixed on the wall，so the wall more stringent requirements， must beabsolutely smooth 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 assistedversion can be bought in this shop， the wall with chuckauxiliary plate， the sucker is arranged in the auxiliary plate， solved.