Square D-brand I-Line circuit breaker power distribution panelboards are for use on AC or DC systems. The panels, labeled cULus (compliance to UL and CSA standards certified by UL) are also Underwriters Laboratories (UL) Listed under File E33139. The following are suitable for use as service entrance equipment such as all main circuit breaker panelboards. I-Line circuit breaker panelboards are available as 4001200 A main lugs only and 1001200 A main circuit breakers. I-Line circuit breaker panelboards are designed, manufactured, and tested to comply to UL, CSA, NFPA, NEMA & W-P standards. This door lock is used with NEMA 1 I-Line Panelboards.