A strip (10) of slips (12) is characterised by breaking portions (62, 64) at which each individual clip (12a, 12b, 12c) is separable from its longitudinal neighbours these portions being coextensive, longitudinally of the strip, with the line of separation (60) which divides off each clip from its longitudinal neighbours and which is formed without removal of material of the strip. This line is achieved by shearing the material of the strip while bowing it about a longitudinal axis so as to present a curved surface to an oncoming shearing tool which has an oppositely curved surface. The extent of intersection of the opposite curve defines the length of the line of the separation. The breaking portion is adjacent each end of the line. The clips during severence suffer apparent laterial contraction but no longitudinal distortion.