What contact between wheelchairs is allowed?

Tackling is by touch only, and the By-Laws restrict contact between wheelchairs as follows:

• Grabbing or holding: grabbing an opponent or their wheelchair is a free kick. Holding includes pushing and pulling, and you may not hold another player with any part of your chair or body so that their movement is impeded.
• Double teaming: sandwiching an opponent between two wheelchairs so their position is locked down is not allowed.
• Charging and bumping: you cannot charge or bump a stationary player recklessly, you must avoid contact where possible when travelling at speed, and you can never bump a player in the rear axle of their wheelchair.
• Rotating a chair: you cannot contact an opponent's chair so it rotates in a way that puts their safety at risk.
• Ramming: a free kick is paid if you continuously pull your chair back and ram an opponent. Initial contact that is not reckless is allowed.
• Push in the back: pushing or bumping an opponent in the back, including the back of the wheelchair, is a free kick.
• Front on contact: forceful front on contact in a marking contest when you are not trying to mark or spoil the ball is not allowed.
• Arm chop: deliberately chopping the arms of an opponent who is marking or passing is a free kick.
• Duty of care: the player second to a contest must protect the hands and head of the player first to it, or a free kick is awarded against them.

You can shepherd a player in possession within two metres, but you must not bring them to a complete stop, which counts as blocking.