How do I add the app drawer button to my homescreen or dock?

I accidentally deleted the icon for the Android app drawer that sits in the middle of the dock. What app is this and how can I add it back?

You can get it back by following 4 easy steps
1.Tap and hold on any empty spot on your home screen.
2.Select “Add” > Then select “Go shortcut” >> Appdrawer.
3.Select “OK”.
4.Now you will see the app drawer icon which you can drag anywhere.
I hope this will help you to get back your app.

For NOVA launcher users the steps to restore or get back missing app drawer icon/button are as follows:-

1.Tap and hold (long press) on an empty space on your home screen.
2.Select “Widgets”
3.From Nova Launcher widgets, long press “Nova Action”
4.You will now be taken to the home screen.
5.Select “App drawer”.