A rheological measurement can be made comprising the steps of disposing a sample to be measured between two opposing surfaces of a fixture; coupling two opposing surfaces of the sample with a corresponding adjacent one of the two opposing surfaces of the fixture to create a secondary sample boundary within the sample; and measuring a rheological parameter of the sample. The two opposing surfaces of the sample are coupled with a corresponding adjacent one of the two opposing surfaces of the fixture by penetrating at least one of the opposing surfaces of the sample with a plurality of protrusions disposed on the corresponding surface of the fixture.