This is my Felder mortising attachment for a jointer/planer. On the top of the mortising table I've got a shop-made fence that is about 4' wide with slots for front to back adjustment and a Mark Dujinski designed flip stop for setting up repeatable mortises.
This is the front view of the mortiser. The dark wood is a piece of Jarrah that I have to show where the work piece would go. The fence actually goes behind the work piece and holds it in place when it's being pushed into the mortising bit. Note that the fence assembly has wings on both sides to hold up long work pieces. The work piece is pushed up to a slight lip on the front side of the mortiser.
This is a rear/side view of the Felder mortising attachment with a shop made 90 degree fence mounted on it. Note the holes in the table which I drilled and tapped to accept the ratcheting levers. These levers I got through Grizzly.