Developed originally by Dr. Clay Thompson. He developed the drop table (Thompson Table) that was fully patented in 1957. He discovered pelvic displacement patterns and a correlation between pelvic displacements and difference of leg length. This analysis can be used to assess more accurately the location of a subluxation depending on the response in the body. The adjustment is assisted by the use of what is known as a drop piece. This drops away gently to assist the removal of the subluxation as the adjustment is made with the patient lying face down.