Kiwav feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in engineering to measure the clearance between two parts.
They consist of 25 of small lengths of steel of different thicknesses with measurements marked on each piece. They are flexible enough that, even if they are all on the same hinge, several can be stacked together to gauge intermediate values.
round tip thickness straight leaf measure hand tool spark gap tappet adjustment engine intake cylinder head valve maintenance check 2 4 stroke spark plug piston connecting rod crankshaft