A security apparatus for securing a portable electronic device comprises a support and a guide positioned within the support and defining a plurality of surface features. At least two holders are partially positioned between the guide and the support and define a plurality of complimentary surface features. A lock assembly is configured move between an unlocked state and a locked state. In an unlocked state, the at least two holders are enabled to move in a first direction that is away from the support and in an opposing second direction to move the at least two holders towards the support. In a locked state, the lock assembly moves the guide to clamp the at least two holders between the guide and the support to engage the surface features of the guide with those of the holders and inhibit movement of the at least two holders in the first direction.