[1][2] The object of pressure immobilisation is to contain venom within a bitten limb and prevent it from moving through the lymphatic system to the vital organs.
The pressure of the bandage should be firm enough that the first aider's finger cannot slide underneath, but not so tight that it cuts off circulation to the hand/foot.
This can be tested by lightly pinching or pressing a toe or finger until it blanches white, then when the press/pinch is stopped, pinkness should return within seconds.
[5][6] The limb is then immobilised by prompting the casualty not to move, or where possible by applying a splint or sling.
Today, it is the recommended first-aid procedure in Australia for treating snake and funnel web spider bites.