An endoscope apparatus for endoscopic treatment is disclosed. The apparatuscomprises an endoscopic insertion tube comprising an outer surface includingan outer rail formed longitudinally thereon and extending along a portion ofthe insertion tube. The outer rail has a predetermined shape. The insertion tubecomprises an inner channel formed therethrough. An endoscope apparatus forendoscopic treatment is disclosed. The apparatus comprises an endoscopic insertiontube without a working channel and an outer surface including at least one outerrail formed longitudinally thereon and extending along a portion of the insertiontube. The outer rail has a first predetermined shape. At least one medical deviceincludes an outer wall having at least one mounting unit formed thereon alonga portion of the length of the outer wall. The mounting unit has a second predeterminedshape cooperable with the first predetermined shape. The second predeterminedshape is formed to complement and slidably cooperate with the first predeterminedshape of the outer rail for slidably attaching the medical device thereto.
