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In page Hammer throw:

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Throws are made from a throwing circle. The thrower is not allowed to step outside the throwing circle before the hammer has landed and may only enter and exit from the rear of the throwing circle. The hammer must land within a 34.92º throwing sector that is centered on the throwing circle. The sector angle was chosen because it provides a sector whose bounds are easy to measure and lay out on a field (10 metres out from the center of the ring, 6 metres across).[3][4] A violation of the rules results in a foul and the throw not being counted.[citation needed]