How do you access the 'Select All' checkbox?

I've got it set up on my grid so that each individual checkbox selects the object present in that row, and that is working. However, when you click the 'Select All' checkbox that Kendo UI automatically provides when you add a columns.Select() to your grid, it only grabs the object present in the first row.

My initial thought was I could set up an event binding that tied back to the ID of that specific checkbox, but when I tried this, I realized the ID for that checkbox was being randomly generated every time, so this strategy wasn't going to work.

I can't use this.selectedKeyNames() as this doesn't refer to the right object in the current context.

Basically, I'm wondering if there's a better way of accessing that 'Select All' checkbox so I can throw some extra code in to grab every single object I have present in my grid.