Source : Webster's Revised Unabridged Dictionary (1913)

Attachable \At*tach"a*ble\, a.
   Capable of being attached; esp., liable to be taken by writ
   or precept.

Source : WordNet®

attachable
     adj : capable of being fastened or added to something else; "a
           handle attachable by two bolts" [ant: {detachable}]