Supports keep structures stable and static by securing them to large rigid bodies, such as a building or the ground. Supports keep structures static by inducing reaction forces, effectively cancelling out any loads applied to the structure. The type of support reaction forces possible with any given support is dependent on what kind of support is used. Some support types can provide a reaction moment, others will not, some can provide a force only in a given direction, while others may allow any direction.
2D Support Types
Cable
Tension force is in the direction of the cable, away from the body.
Smooth Surfaces
Force compresses the body and is normal to smooth surface.
Rough Surfaces
Normal force and frictional force are applied.
Rollers
Force normal to the roller support.
Sliding Glide
Force normal to slider guide.
Pin
Pins that are free to rotate can support any 2D force. If a pin does not allow rotation then it can support a moment as well.
Weld
Welded/fixed joints can support any 2D force and a moment.