The utility model relates to a dedicated triangle ware in the teaching, a ladder groove corner pointer is with adjustable demonstration triangle ware in plane, including three the first fly leafs that the structure size is the same, second fly leaf and third fly leafs, every fly leaf comprises chi board subtotal carousel part, as the improvement: the last profile of carousel part has the protruding roof beam of arch, has the ladder protruding rail on the chi of limit on the plane, there is the ladder recess under the slide on the plane, have pearl seat stand rank hole under the slide on the plane, pearl seat stand rank hole symmetrical arrangement is in the transition groove both sides, plane contact on the outer outstanding sphere of the sliding ball seat lateral surface on the ball that slides on outer half of the outstanding sliding ball seat and the limit chi, and be having on sliding fit, the especially limit chi under corner scale and the slide corner pointer on the back of plane to correspond in that the position is photogenic between the ladder recess on every fly leaf and the ladder protruding rail on the adjacent fly leaf on the plane, control the carousel partly and the rotation angle between the chi board branch possible convenient, directly perceivedly.