An apparatus to secure a ladder to a ferromagnetic support such as an exposed ferromagnetic support comprises a pair of bracket clamping assemblies removably attached to a rung on a ladder. The brackets are pivotally bolted to magnet mounts, which each hold a permanent magnet that releasably holds the ladder in place against the support. The apparatus prevents the ladder from slipping, and further serves to hold the ladder at the proper angle for safe use. The apparatus finds particular application where exposed ferromagnetic metal beams are available in the workspace but tying a ladder for safety would be impractical.