First, pick up the first metal part of the clasp (1), then pick up the second metal part (2) to open the Milanese strap. Place the strap flat on a table, and take the screwdriver (or similar object).
Position the screwdriver in the small notch of the clasp (2) and use it as a lever to release the mechanism of the Milanese strap.
Once the clasp is unlocked, turn the strap and slide the clasp to the desired size, making sure to place it in one of the notches (to allow the clasp to lock).Slide the clasp towards the klokers key (center of the strap) to reduce the size, or towards the outside of the strap to enlarge the size.
To close the clasp, clip the part (2) that you had previously picked up with the screwdriver (always be at one of the notches on the back of the strap).
You can now try your Milanese strap to check the size!