The need to examine the knuckle region of Hanford's double shell tanks (DSTs) has received considerable attention over the past couple of years. Commercial, off-the-shelf systems to examine the knuckle are not available. Preliminary tests at the Pacific Northwest National Laboratory (PNNL) in FY 1999 indicated that a unique technology utilizing ultrasonics could provide a solution to the knuckle examination problem. In FY 2000 PNNL embarked on a study to provide evidence that the ultrasonic technology had the capability to detect and size stress corrosion cracks in the knuckle region of the DSTs. Analysis of the examination results conducted at PNNL in FY2000 provided engineering data strongly supporting a proof-of-principle concept for utilizing a combination of pulseecho Synthetic Aperture Focusing Technique (SAFT) and tandem-SAFT (T-SAFT) inspection methodologies. These methods can be applied to the problem of flaw detection, localization, and sizing in Hanford's double shell waste tank knuckle region and beyond.