Frontline Ladder Safety Walk-Thru Extension* Frontline's Safety Extension Ladder Walk Thru is designed to fit most ladder profiles in the market. It is fully compatible with ladders from Type II to Special Duty Type IAA. * The utilizes a dual clamping safety lock system which improves stability when accessing the handrails of the Walk Thru.. * The height of the Frontline Ladder Safety Walk Thru Extension allows for easier compliance with the proper ladder elevation above the walking surface,