fishing space
The space between the base and head of a rail in which a rigid steel bar is placed.
Fishing space: gap for joining damaged rail lengths
A fishing space is the gap between the foot and head of a rail section, sized to accommodate a fishplate and bolts during field repair or temporary joining of rail. On standard gauge track, this gap typically measures between 8 and 12 millimetres, though exact dimensions depend on rail profile and local standards. The space exists naturally where two rail ends meet, or it is created deliberately when a rail section has been damaged and requires temporary support before replacement.
The fishplate, a rigid steel bar, slides horizontally into this space and bridges across the joint, held in place by bolts driven through pre-drilled holes. The bolts clamp the fishplate against both rail sections simultaneously, transferring load across what would otherwise be a weak point. Without this clamping action, the joint would flex excessively under wheel loads, causing rapid wear and potential failure. A properly fitted fishplate in good fishing space maintains track geometry and wheel guidance until permanent repair or replacement of the damaged rail is possible.
Common problems and maintenance
Fishing space can become damaged through corrosion, impact from derailed stock, or improper fishplate installation. Rust scale and deformation reduce the clearance available, making insertion of a new fishplate difficult or impossible without grinding or chiselling. A space that is too wide allows the fishplate to rock side-to-side under load, defeating its purpose. Track workers must measure fishing space regularly on older sections of line, especially where temporary repairs have been made.
The term originates from the practice of using fishplates, named after their resemblance to the backbone of a fish, which was a nineteenth-century innovation for joining rail ends. The vocabulary persists even though modern welded rail and continuous welded rail (CWR) have reduced reliance on bolted joints in mainline track. On legacy branch lines, sidings, and heritage railways, fishing space and fishplates remain essential equipment for rapid repair and temporary restoration of track geometry.