force to be exerted by the operator and if the vibration isolation device between the operator handle and the exciter is too soft control becomes difficult on the other hand if the vibration isolating device is too hard then the vibratory forces transmitted to the operator become too great the blade 11 is demountably attached to the bottom of the exciter mechanism 12 such that the working face 16 of the blade faces the operator grasping the handles 15 whereby the screed is pulled over the surface of the freshly poured concrete as best seen in fig1 and 3 the upper edge of the working face 16 of the blade 11 is provided with a horizontal mounting rib 17 that is received in a groove 18 in a casting that comprises a lower exciter housing 20 the front of the blade 11 also includes an upper horizontal mounting rib 21 over which a pair of mounting clips 22 are attached to the housing 20 with machine screws 23 to clamp the blade 11 to the exciter housing 20 referring also to fig2 the engine 13 is mounted vertically above and directly to the exciter housing 20 and includes a direct.