inspect tire tread depth

https://alpha-wiki.win/index.php/How_to_Prepare_for_MOT:_A_Practical_Guide_from_an_Experienced_Mechanic

To inspect tire tread depth, grab a quarter and place it into the groove with Washington's head facing down; if you can see the top of his head, it's time to replace the tire. Also look for uneven wear or any bald spots that could reduce grip on wet roads.