栅 pronunciation - zhà vs. shān
The pronunciation shān is only really used in certain compound words: 


光栅/光柵, a diffraction grating used in optics. 
栅极/柵極, the grid of a vacuum tube or the gate of a transistor.


The Taiwan standard uses zhà for both even in this context.

Apparently, it also has another pronunciation, cè, for certain placenames in Zhongshan, Guangdong.