ARFAS (Aluminum Rail Fall Arrest System). Red Steel Building installation. ARFAS was installed using purlin mounted twin arms to lower rail below roof obstacles. Each 2 user system was installed over each of the 6 modular trailer maintenance bays. Skyloc II SRL’s installed on ARFAS trolley’s to limit fall clearances to 4’, including 2’ maximum extension, 1’ harness stretch and 1’ safety factor.