The Dog Worker has a removeable spinning wheel on the top that you have to turn to 'unlock' the pegs, then slide the pegs to release them to get the treats under the pegs. It also has four pegs that need to be lifted up to get to the treats.
Since Rach is young, Mum removed the spinning wheel on the top to make it a little easier and didn't slide all of the pegs. Once Rach masters his first 'level' she can increase the difficulty for him over time.
The key, again, for this puzzle is for Rach to 'use his mouth' to lift the pegs, so Mum refreshed Rach by holding the pegs and when he would bite them, she clicked and treated. Then she put them on the toy and Rach picked them up with his mouth right away. So Mum loaded up the puzzle with treats and leg Rach go at it.
Here's the vid....we think he did just great!