When working in the Dynamic Block editor there's situations where you'll need to hookup a stretch action to a linear parameter. And you only want a grip on one side to allow users to only stretch the block in one direction. Well in order to accomplish this, you need to think a little bit a head in your Dynamic block creation. If you want the extra grip to disappear you need to select the parameter. Then in the properties palette under Number of grips, specify here how many grips you want to show for this parameter. Another little tricky thing about how the Dynamic Block grips work, is how you specify your parameter grip points. If you have a linear parameter and select the first point for the parameter at 0,0 then the second at 0,10. You'll see two grips enabled. Then select the parameter and change "Number of Grips" to one. You will see the bottom grip disappear and only show the top grip. So, for LINEAR & POLAR parameters the first point you specify for you parameter would be the grip that disappears once you change the "Number of Grips" to one.