What procedure should be followed if the SFRM is too hard to insert the thickness gauge directly?

When the Sprayed Fire-Resistive Material (SFRM) is too hard to allow for the direct insertion of the thickness gauge, drilling small-diameter holes is the most appropriate procedure. This approach allows the technician to create an access point for the gauge, ensuring accurate measurement of the coating’s thickness. By using drilled holes, one can obtain the necessary data without compromising the integrity of the SFRM or risking damage to surrounding areas.

Moreover, drilling is a precise method that offers a way to bypass the challenge presented by the material's hardness, enabling the technician to perform a thorough assessment while also maintaining control over the measurement process. Other methods, like using a larger probe or soaking the SFRM, may not yield accurate readings or could alter the material properties unnecessarily. The option of using a hammer could result in unintentional damage and does not align with the best practices for measuring thickness. Thus, drilling small-diameter holes is a practical and effective solution for this scenario.