I know, somehow that sidebrush screw came loose from the side brush module and disappeared from view.  Here's an offer to consider if you don't want a modded side brush.  You can order a set of (2) stock side brush screws for your Roomba @ $3.50 that includes USPS shipping.  Just paypal $3.50 to e_vickery@bellsouth.net and mention what you are wanting....               

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Just click the Buy Now button below to have a set of screws shipped to you