Nikki’s trick for keeping kids close at hand in the parking lot:
My son’s car seat was on the gas tank side of the car. My daughter was learning her shapes at the time. I’d turn getting into the car into a game of tag by making her "touch the square" until I got her brother safely into the car. I could use two hands to put my son in his car seat while watching my daughter stay put touching the cover to the gas tank. Then when I had my son all buckled in, I would grab her hand and walk her over to her side of the car.
She is four and still plays this game. It also works at the store when you need a free hand. Spot an item with an easy-to-identify shape and color and ask them to touch it to keep them close to you while you write a check.
Related: "Ground tie" your child