Stationary Front
A stationary front is represented on a map by triangles pointing in one direction and semicircles pointed in the other direction.
L.S.Gardiner/UCAR
A stationary front forms when two air masses of different temperatures push against each other but neither is powerful enough to move the other, causing the front to stop moving. On a weather map, a stationary front is shown as alternating red semicircles and blue triangles.