Hammer and Discus Cages: Dimensions, Safety and World Athletics Rules

Hammer and discus are the athletics events with the highest safety risk. Cage dimensions, netting and gate panels are defined by World Athletics rules to stop the implement reaching spectators and other athletes.

Discus and hammer are heavy implements released at great speed after the athlete turns in the circle. A poor throw can send the implement in an unexpected direction. The throwing cage is the key safety equipment that stops it leaving the sector and protects officials, athletes and spectators.

Throwing circle and sector

• Discus circle: inner diameter 2.50 m.
• Hammer circle: inner diameter 2.135 m. In combined cages a reducing ring is placed inside the discus circle for hammer.
• Sector angle: 34.92°, with sector lines starting from the centre of the circle.
• Circle surface: concrete, smooth and non-slip, 14–26 mm below the surrounding level.

Products: discus metal ring, hammer fibre reducing ring.

Discus cage

The discus cage is C-shaped in plan and made of at least 6 panels. Netting or panels are at least 4 m high. The cage mouth is about 6 m wide, positioned in front of the circle centre. Netting is hung so that the implement does not rebound and does not strike the cage posts directly.

Hammer cage

Because the hammer is a heavy ball on a wire, it needs higher and wider protection than discus. The rear panels of a hammer cage are at least 7 m high, and at the mouth there are two movable gate panels up to 10 m high that open or close according to the thrower's direction of rotation. They are set for right- or left-handed throwers to narrow the danger zone.

Where one cage is used for both events (combined cage), it is designed to hammer requirements and the circle is changed with a reducing ring for discus. Product: hammer and discus cage.

Netting and structure

• Netting: high-strength natural or synthetic fibre with a mesh size that absorbs the implement's energy.
• Posts: galvanised steel or aluminium, fixed with base plates or sockets. Wind load and net tension must be checked structurally.
• Net–post clearance: netting must hang far enough from the posts that an implement hitting it does not reach a post.
• Gate panels: easy to move, lockable and designed not to swing in the wind.

Siting and safety

• Throwing areas are sited away from runners on the track and spectators, with the landing sector facing into the stadium.
• The sector must have a surface (grass or suitable synthetic) where the implement leaves a mark and can be measured.
• In training, gates must be in the correct position for every throw, and the sector entered only after the throw.
• Netting should be checked at the start of each season and regularly for tears, slack and UV wear.

Indoor shot put

Indoors, the shot put area is enclosed with netting and a stop board is used so the shot does not damage spectators or hall equipment. Products: indoor shot put cage, shot put stop board.

SFS Engineering manufactures and installs throwing cages to World Athletics rules. For all field dimensions see athletics track dimensions, and our full range on the athletics equipment page.

Frequently Asked Questions

How high should a discus cage be?

Netting or panels must be at least 4 m high; the cage is C-shaped in plan with a mouth of about 6 m.

Why is a hammer cage higher?

The hammer is a heavy ball on a wire and can fly higher and at wider angles. Rear panels are at least 7 m and the front movable gates up to 10 m high.

Can hammer and discus use the same cage?

Yes. A combined cage is designed to hammer requirements, and the circle is changed with a reducing ring for discus.

What are the discus and hammer circle diameters?

The discus circle is 2.50 m and the hammer circle 2.135 m inside diameter.

Get technical support for your project: SFS Engineering handles site survey, design, material selection and installation as a single contractor. Send us your dimensions and site details through our contact page and we will work out the right solution together.