Such a test is not valid and should always be culled.

If the grain is diagonal or the stress is unevenly applied a diagonal shear may occur from top to bottom of the test specimen.

Such tests are also invalid and should be culled.

When the plane (or several planes) of failure occurs through the body of the specimen the test is valid.

It may sometimes be advantageous to allow the extreme ends to dry slightly before testing in order to bring the planes of failure within the body.