The invention relates to a method for producing and checking a thread arranged in a cylinder head to receive a spark plug. However, the invention also relates to a device for checking the thread introduced into the cylinder head.By defining a starting point of the internal thread to be produced specifically in terms of position thereof within the parent hole by using spark plug parameters, the spark plug will always be aligned with its spark gap oriented toward the injector. For the purpose of checking, use is made of a plug gage, the screw-in thread of which has the parameters of the spark plug thread and with which, by using a measuring face, the position of an extension on the threaded body can be established. The extension simulates the ground electrode of the spark plug.