Abstract: A portable ladder assembly adapted to be removably mounted in the space between a body and a rail spaced therefrom, e.g. between the body of a conventional truck trailer and tie down rail. The ladder has a main ladder section having an elongated vertical support member and a plurality of step members transversely secured thereto. Means are disposed adjacent a top end of the elongated member for removably securing an upper end of the main ladder section in the space between the body and the tie down rail. Extension members are provided for extending the ladder above the rail to facilitate personnel climbing on the ladder assmbly. An optional lower ladder section having at least one transverse step member supported by at least one elongated member attached to the main ladder section adjacent a lower end thereof is repositionable between at least two different elevations.