A joint web is a special property of joint on Powder Game 2, in which a large quantity of joined elements support each other and form a large, hovering mass that does not fall or otherwise move unless dragged. A joint web can either be created through a large, single mesh or strand of joints being pushed into a small space, or through many separate small joint pieces being pulled into one location.
How it works
A joint web is somewhat paradoxical.
It works because elements cannot push other elements, including joined elements. This allows a joined dot to fall onto another joined dot in such a way that it is supported by the bottom joint. Normally, the bottom dot would simply fall, thus allowing the upper dot to fall, however the bottom joint is supported by the dot above the bottom dot, allowing the top dot to rest upon the middle dot, which in turn is suspended by the bottom dot, which is being held by the top dot through joint.
A simpler explanation is the bottom dot keeps the middle dot from falling, and the middle dot keeps the top dot from falling. Since the top dot is kept from falling, it prevents the bottom dot from falling as well (since they are jointed), thus suspending the entire web in the air.
Despite this rather complex set of requirements for functioning, a joint web can easily be created by simply selecting a high pen-size and dragging a large pile of joints.
Similar effects in other games
In Monster Box, it is possible to create a large, gravity-defying mass of delta-feathers. This suggests that delta-feathers are only solid on each corner, and are thus capable of the same effect in large amounts.