Elongated workpieces such as structural profile members are machined on apparatus suitable for drilling holes or performing other operations at predetermined points by equipment comprising a support with rollers on which the workpiece can be displaced, said support comprising a portal member spanning the workpiece and embodying a tool-carrying cross member having suitable driving tool spindles. The workpiece is located on the support rollers and held in position by vertical and horizontal guide rollers on the portal unit which are pressed into engagement with the workpiece. The cross member which may carry drills or the like is operable towards the workpiece with a cutting feed by means of hydraulic piston devices, and locating means are provided for correctly positioning the workpiece on the rollers. Lengthwise positioning of the cross member is effected by means of an indicator device with a floating zero system which is operated by the displacement of the portal member on the support and is thus available for determining the position of the portal member for effecting drilling at the required points of the workpiece.