Rail spike

In rail terminology, a spike is a large nail with an offset head that is used to secure rails or tie plates (or baseplates) to ties in the track. Spikes are driven into wooden ties either by hammering them with a spike hammer by hand, or in an automated fashion with a spiker.
Many railways use large wood screws, also called lag screws, to fasten the tie plates (or baseplates) to the railroad ties. Machine screws (or bolts) are also used to hold fishplates on jointed rail.

The presence of the letters HC (high carbon) on a spike's head indicates that the spike contains about 0.40% carbon.