The M6 cabinet knock-down fitting system is well-known and widely used as it is a simple, yet effective way of assembling furniture that may require dis-assembly in the future and is attractive so if it must be visible, will not detract from the appearance of the furniture.
The cross dowel nuts will work with the M6 knock-down demon bolts as well as any standard M6 threaded bolt. Simply side-drill a 10mm hole and slip in the cross-dowel, use the slot on the end to align with the bolt hole coming through at a 90º to the cross-dowel and then bolt together the second work-piece.
Available in two overall lengths for most standard thicknesses in zinc-plated finish, they are sold individually.