A support body (7) for an apparatus having an extended nip (N) that is defined by a contact surface (13) of the support body and an opposed surface (4), the support body having two side surfaces (69, 70) facing from each other and connecting to the contact surface, and a bottom surface (71) facing from the contact surface, the support body being arranged to be moved towards the opposite surface by means of a loading system in order to load the nip via the contact surface. According to the invention the support body is elastically deformable and has its contact surface adaptable to the opposite surface in interaction therewith. The invention also relates to a holding device for such a support body and an apparatus, e.g. a press, for the treatment of a fibre web, said apparatus having such a support body. Furthermore, the invention relates to a method of forming the extended nip in said apparatus by loading the support body by means of the loading system, as well as a method of controlling the load in the extended nip by designing the support body with at least two layers with different elasticity providing a corresponding load profile.