"A pad spacer specific to your brakes is very handy to keep around
This is needed for travelling without your wheels in place, but a pad spacer is also perfect for re-setting the brake pads before adjusting them, or after an accidental squeeze of the lever with the wheel out.?
Many tool brands do offer a workshop version of this, called a piston press. They are useful in a shop, but realistically don’t achieve more than what can be achieved with the free plastic version.
These plastic pad spacers will often come with your bike or brakes, but politely asking your local shop mechanic should get you one too."
Very handy indeed @Jeff Backes! Don't lose those If someone 'accidentally' presses that brake lever on a hydraulic brake after you remove a quick release wheel, the pads freeze together. That requires a minor brake bleed to pull the pads apart/relieve pressure on the pistons , something that's handy to know how to do (constant exposure to hot temperatures can also freeze those brakes) but in many instances means handling a fairly toxic brake fluid. If you don't have the ready made plastic separators, a fairly thin wooden shim or folded over piece of thick paperboard make decent substitutes in a pinch.
Transporting a bike with hydraulic brakes without a spacer is a risk, since it's all to easy to have one of those brake levers actuated while loading or unloading a bike or piling more bikes into a vehicle or driving over a bumpy road.