Start by attaching two rack gears to the post.

Next fabricate a halved trolley.

<sup>Rear Trolley

Front Trolley</sup>

You'll need a couple pinion gears that can mesh with the rack gears.

And a couple pins to allow the gears to spin.

Next assemble the trolley. You can use cotter pins through the gear pins to hold everything together You'll probably want to use 4 cotter pins for each gear pin. One on the front of the front plate, one on the back of the front plate, one on the front of the rear plate, and one on the back of the rear plate.

^{Cotter pins not pictured}

Finally, install a spring loaded release pin (held in place using a C-clip), that will lock the trolley in place.

^{Spring not pictured}

When you want to raise/lower the monitor, pull out the release pin, move the monitor, then let the release pin spring back locking the monitor in place.

Start by attaching two rack gears to the post.

Next fabricate a halved trolley.

<sup>Rear Trolley

Front Trolley</sup>

You'll need a couple pinion gears that can mesh with the rack gears.

And a couple pins to allow the gears to spin.

Next assemble the trolley. You can use cotter pins through the gear pins to hold everything together You'll probably want to use 4 cotter pins for each gear pin. One on the front of the front plate, one on the back of the front plate, one on the front of the rear plate, and one on the back of the rear plate.

^{Cotter pins not pictured}

Finally, install a spring loaded release pin (held in place using a C-clip), that will lock the trolley in place.

^{Spring not pictured}

When you want to raise/lower the monitor, pull out the release pin, move the monitor, then let the release pin spring back locking the monitor in place.

For a simpler design. Go take a walk through your local hardware store, and pay close attention to the mechanisms used to raise and lower the table on drill presses.