Ok - about "project next pt" for clines.

This is basically for matching a height relative to an existing object. Again you can accomplish the same thing with other methods, but this method is more convenient when used at the right moment.

So let's say you have a block and you're drawing a cylinder next to it:



As you're tracking the cylinder up along the z axis, you think "hey, I wish I could snap the end of the cylinder to be the same height as this nearby block". But if you move your mouse over to the block, the cylinder slants towards that direction.

So what you can do is drag out a cline that is going in that same z axis direction (the specific endpoint locations of it are not important in this case, just get it going in the same direction), and turn on "Project next pt". Now the end point of that cylinder that you are drawing will be locked on to that z axis line, and you can move your mouse over and snap on to one of the points on the block to obtain its same relative height:




I've been meaning to do one of those screen capture videos to show all the uses of construction lines, because there is an awful lot of stuff you can do with them, not all of which is really immediately apparent.

Of course you can get by without using them at all as well - it's just that in the right situations they let you do things really quickly "in place" without needing to draw extra lines or move things around later, etc...

- Michael