Most homes have a ruler on hand that can, in many cases, provide relatively accurate measurements. For irregularly shaped objects, it may be difficult to use a ruler. But if the object is flat on at least two adjacent sides, rulers work fine in a pinch:
Simply lay the object on its flat edge, move one side to line up with the 0 mark, and measure the other side of the object. It's not the best method for measuring complex shapes, but sometimes a ruler can be enough.