If it's the same as my V700, there are four little plastic plugs covering up the screws. They are flush with the plastic sorrounding the scanner glass. Each plug has a V shape on them, if I remember correctly there's a notch in the walls of the plugs, hidden from view at the point of the V and you can wedge a small screwdriver in there to pop them out. Then you will have access to the four screws and can take off the glass and clean to your hearts content.