Hi Julie,
The 860 machine needs a set of rails over the back rail in order for the garter carriage to work. These rails were supplied with the KG88 but I don't know if they came with the Mark 11.
The Garter Carriage has to be fitted with two magnets in order to work on the 910 machine. If you look at Scanthecat you will find lots of information about Brother machines.
Sue, January 2014