Are you referring to hachures, typically used (in US maps, at least) to indicate depressions in terrain contours? Or are there other kinds of spikes or symbology (like you might see on maps showing fault zones and dips and strikes and such)? If they are simple line hachures or spikes than you could use a hashed line - look at a railroad line style in the Esri stylesets that has a straight "crossbar" for an example of how that is done. You'd just have to make sure the spike fell on the correct side of the line rather than across the line - tip: I think you'd use an offset on the hachure symbol to do that, and would probably need to make sure the direction of the line went the right way for each case. Another option might be to use a picture marker or character marker on a line in the case of "spikes" that aren't a simple short straight line. And a third option could be to use representations symbology, but that gets more complicated if you're not familiar with that functionality (lots of power and user options, but more complex, too).