Abstract: An instrument for cutting paper or similar planar sheet material is provided which comprises a cutter blade mounted in a head portion for rotation about an axis, an elongate handle portion and a neck portion connecting the head portion to the handle portion.The handle portion extends at an acute angle with respect to the axis of rotation of the cutter blade whereby, when the instrument is in its position of use with the cutter blade in contact with a sheet to be cut and the axis of rotation of the cutter blade substantially vertical, the axis of rotation of the cutter blade and the longitudinal axis of the handle portion, when extended, intersect at a point on the opposite side of the planar sheet from the cutter blade and spaced therefrom.

Abstract: A polygonal element is provided for forming polyhedral structures, particularly for use as an educational constructional toy. The polygonal element has side margins each comprising an inner edge, an outer edge, first and second projections extending outwardly of the outer edge and a recess defined by the first and second projections. The first projection comprises a pair of spaced limbs unconnected at their outer ends. The side face of the recess defined by an inner limb of the first projection is an abutment face. One of the side faces of the recess opposite the abutment face and the outer side face of the outer of said limbs is provided with a projecting hinge pip and the other with a corresponding hinge socket.

Abstract: The invention provides an epicyclic change-speed mechanism comprising a fixed outer ring having an inwardly directed running surface, a spider member mounted within the outer ring and rotatable about an axis concentric with the axis of the outer ring, the spider member having a hollow output shaft concentric with said outer ring, an input shaft concentric with the outer ring, and at least one planet wheel contained within an aperture in the spider member, the or each planet wheel being in driven engagement with the input shaft and in rolling engagement with the running surface of outer ring.The invention also provides a model clock incorporating the change-speed mechanism, the face of the clock being formed from interfitting pieces of a constructional toy.