Securing an aftermarket subwoofer

[Vitalvince]

Hey guys,
For those whose have aftermarket subwoofers, how did you secure your subwoofer from sliding around when driving?

 

[PDXSchrammie]

I got this for one 10 inch sub-- http://www.wickedcas.com/home.php?cat=18

 

[teemoney]

Screwed in a couple L brackets