The ideal engagement of a pack into a scrum is a simultaneous movement in the hit, shunt and drive. It is the instantaneous force exerted that makes the difference not the sum of all the forces over time. Even small packs that co-ordinate in this fashion and hit 'on the beat' can control their scrums consistently. The purpose of the scrum machine is to provide teams with a safe tool with which to improve the strength and skills of their players.
A similar piece of equipment called a blocking sled is used by American football players.
Scrum machine types
The most common types are either the sled or the roller.
However, there are others, often for specific purposes or needs.
- Bespoke - numerous homemade scrum machines are in use.
- Indoor 
- Junior - For training children.
- One-man - Against which forwards, rather than a pack, can practice their scrum skills.
- Portable - often abled to be folded down, and with a container on the back which can be filled with sand or water to bolster weight.
- Trailer - which can be attached and detached from a vehicle.
- "Team Scrum Machine". School of Engineering and Physics, University of the South Pacific. Retrieved 2010-05-17.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
- "Effective Scrummaging" (PDF). www.rugbyottawa.com. Retrieved 2010-05-17. Italic or bold markup not allowed in:
- "Indoor Scrum Machines". Retrieved 2010-05-17.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
|Look up Scrum machine in Wiktionary, the free dictionary.|
- Fiji Rugby Scrum Machines
- The Agile Scrum machine
- The Hurricanes' forwards hit the scrum machine
- Assessment of Scrummaging Performance
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