To fix a thing in place so it can be used, and to bring it into a running system. Both make a thing present and held.
Old French monter (to go up, to climb), from Late Latin montare, from mons (mountain); to fix a thing in place so it can be used, and to bring it into a running system.
The act that makes a thing present to a running system — fixed where it can be reached rather than merely existing somewhere nearby.