An interlocking spur
is a natural feature which occurs in a river's upper course, where upward erosion is the dominant force in determining the river's course. As the river wanders between banks that are far apart, the promontories of the hills tend to jut out into the river valley in a staggered formation, interlocked together in a formation like the teeth of a zip. These promontories are referred to as interlocking spurs.
While similar in general appearance, the mechanism behind the formation of interlocking spurs is different than that behind
If the valley experiences glaciation, the interlocking spurs are foreshortened as the tips are sheared off. These sheared spurs are referred to as truncated spurs.