Wedge
A wedge is a non-damaging "weapon" that is used to get underneath the opposing robot. This is a major advantage to have, as most robots are helpless when you are underneath them. This then gives you the chance to Gut-rip, or grind at you opponents vulnerable undersides. Most bot designs in both Stock and DSL should have basic wedges, while bots such as flippers, Popups, and other wedgebots should have more advanced wedges.
Wedge (bot type)
Real examples: Bad Attitude
Game examples: Ronin, Lil'Dog
Wedges are a simple bot design, and efficient if used well. It is basically a robot with a sloped front and a low ground clearance, for getting under other bots. Powerful drive train helps, too.
PROS
-Fast
-Easy to build
-Can control another bot by taking away it's drive train
CONS
-Very low damage for most of them
-Weaker when inverted
Wedge (robot feature)
A wedge shape are not everything in RA2 - again any other wedge bot, you must add some components that will give you the edge. This robot feature is called "wedge" too.
Stock
There is basically only one type of good wedge for stock, and that is putting a small wedge (with an extender) on a burst motor (like if you were building a flipper) and lowering the burst motor to its proper location. You can however, have more complicated burst motor designs which will increase your wedginess.
DSL
In DSL however, there are quite a few successful types of wedges.
The most common are skirts mounted on skirt hinges. Polycarbonate skirts are most commonly used here. You can then rotate the hinge like a burst motor into the proper position.
This kind of wedge is found on most DSL AI and is the commonly used wedge.
Another type is a skirt mounted on a metal hinge. Metal hinges cannot be rotated like a burst motor, and must be wired to move. When lowered flat up against the ground, they are much more efficient than classic skirt hinge wedges, can also go under Mako-style wedges and are just a little less efficient than snapper wedges. Rarely used (although more than MCB wedges), mainly by Urjak's Flipper and RAW entry Lousy Launcher, and then on several of Naryar's wedged bots.
There is also a third kind of wedge, called the Mako-style wedge or axle wedge. This kind of wedge has become popular in recent times. The flail wedge is made by putting a skirt on an axle mount. It is best to mount the axle onto a static support. Also, they're more efficient if flat against the ground. A weakness to this design however is that if you move to fast, the skirts may lift off the ground, giving your opponent a chance to hit. The axle wedge was developed by Jules. (See the robot Mako or Diarrhea of a Madman for a good representation of the flail wedge.)
Heavier than the usual wedges, these are normally superior to hinged wedges, but are less efficient against fast bots even with classic skirt hinge wedges (and this is why Enfilad3 and Hazardous Contraption could go under DOAM]] head-on).
Another fourth kind (rarely used) are called "Morse Code Breaker" or "MCB" wedges, because they were first used by MetalikVyper in RAW with his bot, Morse Code Breaker. They use the odd collision mesh of the skirt hinge to make a wedge, but haven't proved anything yet. They are also used on Somebody's GUMBA entry, Cutinator. These are the lighter wedges.
The ultimate wedge in DSL is still the snapper wedge, like in Stock. You simply attach your wedgy part to any burst motor (a sheet of any sort or a extender/small wedge combo) and you can get under anything (excepted a better snapper wedge). However, these are by far the heavier of the wedges.
It also seems that the small wedge component is a great choice for any wedge, but they're heavier, bigger and weaker than classic metal skirts for the same weight and size.