Hobbling a horse is a necessary skill for long riding. There will be times when there is simply nothing to tie the horse to! Hobbles are also good for allowing the horse to graze without a rope to get tangled in.
They do have limitations, especially for smart horses like Apollo who figure out how to move fast while wearing them. They are not normally left on overnight for this reason - a hobbled horse can travel a great distance when left unattended that long!
There are many good videos on youtube about how to train a horse to wear hobbles. Basically, you start in an arena with soft footing so the horse's knees don't get injured when he falls. And he will fall while he figures it out. Just stay out of the way and he'll get his balance back quickly.
After the initial surprise of having the feet tied together, the horse must learn to move in hobbles. They can shuffle around and graze comfortably once they figure it out. Apollo prefers to hop. But he has only practiced with them a handful of times, so maybe he will learn to shuffle some day too.
There are many types of hobbles. Apollo's are nylon with padded cuffs and a nice quick release buckle on each cuff.