I have to repair a Garage door frame by grafting in new bottom sections to the jambs. I like to do this with halving joints but they are always a bit awkward to cut on the existing vertical timbers. I was looking at Paul sellers woodworking site and happened upon a design for a "poor mans router". It was made with a piece of scrap oak, a bolt and an allen key. As I needed it for tenoning I modified the design. I decided to make it about 11 inches long with a cutter offset towards one end. I planted an additional piece of timber on the front of the long end to make it easier to use. The whole thing took about 2 1/2 hours to make and it was well worth the time. I cut the joint and pare out most of the waste then just finish the cut with the router giving a perfectly square and acurate joint. Not being as skillful as Paul even I can make a decent job with this.
You can check Pauls site out at http://paulsellers.com