Originally Posted by sch

Not in front of the bike now but if the hood is lifted along the outside a groove in
the side of the metal should show up. On my 105/Ultegra levers, both have the
groove and a 5mm allen wrench slid down the groove will engage an allen head
bolt that loosens the shifter. Look under the outside hood for a groove. The shifter
may stick a little but rotating it back and forth should loosen it and allow removal.
Shimano has PDF versions of the user literature on their web site for reference.
Steve