[header] How to install a door latch attached mortise plate [title] Place the latch [or just the mortise plate] in place on the edge of the door. [step] Make sure it is centered on the cross bore hole and mark the perimeter with a pencil. This will allow you to know exactly where to chisel out the wood of the door so that the mortise plate fits nice and flush on the surface. 
You want the mortise plate to be flush. If it is not, the door will likely not shut correctly, or may not close at all.