If you need to space points or objects equally along a straight line or simple arc, the Array command can provide a quick and easy way to do that. But what if your path isn't a line, arc, or circle?
The Measure command (available at the command line, under Draw-->Point-->Measure, or on the extended Draw panel of the Ribbon under the Point pull-down) places points or blocks at specified intervals on an object.
In the next image, I ran Measure on the spline with an interval of 3. PDMODE is set to 35, so you can see the points.
You can also use Measure to place blocks instead of points. You can choose to have the blocks be inserted with no rotation...
...or rotated so that their horizontal lines are tangent to the path at that point.