A ladder comprising: a first assembly having a pair of inner rails and a pair of outer rails, the pair of inner rails being slidably coupled with the pair of outer rails; and at least one locking mechanism coupled to an outer rail, the at least one locking mechanism including: a lever and an engagement pin coupled therewith, the lever being located and configured to pivot relative to the outer rail such that, upon application of a force by a user to a first portion of the lever in a first direction towards the outer rail, the engagement pin is displaced in a direction that is different from the first direction, wherein the lever is configured to be selectively positioned between a first position, wherein the engagement pin engages an opening in an associated inner rail, and a second position, wherein the engagement pin is retracted from the opening of the associated inner rail; and a biasing member configured to bias the lever towards the first position; characterized in that the at least one locking mechanism includes a retaining mechanism configured to maintain the lever in the second position until application by a user of a predetermined force in the first direction to a second portion of the lever, wherein the pivoting point of the lever is situated between said first portion and second portion of the lever. a first assembly having a pair of inner rails and a pair of outer rails, the pair of inner rails being slidably coupled with the pair of outer rails; and at least one locking mechanism coupled to an outer rail, the at least one locking mechanism including: a lever and an engagement pin coupled therewith, the lever being located and configured to pivot relative to the outer rail such that, upon application of a force by a user to a first portion of the lever in a first direction towards the outer rail, the engagement pin is displaced in a direction that is different from the first direction, wherein the lever is configured to be selectively positioned between a first position, wherein the engagement pin engages an opening in an associated inner rail, and a second position, wherein the engagement pin is retracted from the opening of the associated inner rail; and a biasing member configured to bias the lever towards the first position; a lever and an engagement pin coupled therewith, the lever being located and configured to pivot relative to the outer rail such that, upon application of a force by a user to a first portion of the lever in a first direction towards the outer rail, the engagement pin is displaced in a direction that is different from the first direction, wherein the lever is configured to be selectively positioned between a first position, wherein the engagement pin engages an opening in an associated inner rail, and a second position, wherein the engagement pin is retracted from the opening of the associated inner rail; and a biasing member configured to bias the lever towards the first position; characterized in that the at least one locking mechanism includes a retaining mechanism configured to maintain the lever in the second position until application by a user of a predetermined force in the first direction to a second portion of the lever, wherein the pivoting point of the lever is situated between said first portion and second portion of the lever.