Building the jaw.

Step 1 Obtain the arm, prepared earlier, as well as the two jaw pieces, 4 spacer rings and a large axle. These are shown on the right..

Step 2 Place the arm on a level surface and position two spacer rings under the large holes at the end of the arm. Pass the large axle through the large hole at the tip of the arm and through the two spacer rings and out through the other side. Click to see what it should look like

Step 3 Once the large axle is fitted through the holes and through the two spacer rings slide a spacer ring on either side of the large axle.

Step 4 Slide a cardboard jaw on either side of the large axle. Click to see how the jaw of hydraulicus should look like.

Step 5 Slide a large ring along the axle on both sides and glue the ring onto the axle.

Step 6 Now take the arm, two small rings and a thin axle, as shown on the right.

Step 7 Pass the thin axle through the two small holes on the jaws. Slide two small rings on either side of the axle and glue the rings to the axle. This will provide support for the jaws as they exert a force to grip items.

Click to see how the arm and jaw should look like so far.