Once you know the conformance standards and specifications that your caliper is supposed to align with, it is important for you to verify that conformance. One way to test the partial surface contact error conformance of your caliper gage uses gage blocks, a caliper checker, or another reference tool. Using at least three and at most five testing points, you will want to cover a minimum of 90% of the measurement range of the tool and to locate the reference standard tool along different positions of the caliper gage measurement faces. Testing the scale shift error conformance on a caliper gage similarly uses a caliper checker or gage blocks, but may also be done with a ring gage or surface face. What reference standard you use will vary depending on whether you are checking step, depth, or inside measurements. For guidance on choosing test points when calibrating and verifying your caliper gage, refer to the ASME B89.1.14. When doing this process with a used instead of a new caliper gage, just be sure to also check for wear and damage.