C.R. LAURENCE SB202 CRL Andersen Knife Latch. CRL"s Cat. No. SB202 Knife Latches are designed to hold screen frames into Andersen Windows. The screen and window frame are first notched with a Cat. No. WST901 Notching Tool, and then the Knife Latch is inserted into the screen frame. Each pack contains one right hand and left hand latch. Minimum order is one pack.. Part Numbers Variations: SB202