Four Bolts And A Wire

Shimano doesn't include an ISO to post mount adapter with their brake sets for two reasons: 1) Not all frames need an adapter  2)  The adapters are rotor size specific.  Even if they decided to include an adapter, they would need to include at least three different sizes.

Two M5 bolts, complete with pre-applied thread lock secure the adapter to the frame.  Shimano also supplies a thin wire to help keep the bolts from loosening.  The wire gets wound counterclockwise around each of the two bolt heads.  Should one bolt try to loosen, the taut wire would pull the other bolt, essentially trying to tighten it.  I'm not really sure why the friction against the wire is better than the friction against the adapter itself, but Shimano seems to think the wire helps.

Perhaps difficult to see in the picture, but the bolts where the caliper attaches to the adapter, remain loose.  They will get tightened once a rotor slides between the brake pads as part of the final brake adjustment.