Chris Rogers sends in this question about guides:
Is there a way to create a guide at a specific point? Eg, a vertical guide at 167 pixels? Or a horizontal guide at 83 pixels? I’m thinking more like a non-traditional number/not on a number point that can be snapped to on a grid by dragging it out. Seems like I remember a way to click somewhere and enter a number and program creates it for you? Photoshop?
This is a great question, only because it provides a wonderful opportunity for me to also explain a change that was made in Illustrator CS3.
First, let's talk about Illustrator CS2 (and just about any version prior to that). Guides are really objects. When you drag out a guide, you can simply use the X and Y coordinate fields in either the Transform palette or the Control palette (at the top of the screen) to reposition those guides numerically. But there's a catch. By default, guides are locked. Meaning that when you initially drag out a guide, as soon as you release it, it becomes locked. And locked objects can't be selected. So what you must do is first unlock your guides (it's easily available by just right-clicking on the artboard). Then you can select a guide and reposition it numerically.
I should mention that InDesign's guides can also be repositioned this way, but the guides are unlocked by default -- making it easy to quickly drag out a guide, punch in a value, and move on.
I should point out that in both InDesign and in Illustrator as well -- since guides are objects, you can also copy and paste guides (or use the Align functions on them). Of course, all while they are unlocked.
WHAT CHANGED IN CS3?
In Illustrator CS3, guides are UNLOCKED by default. That means you can drag out a guide and immediately punch in a coordinate in the Control panel. Which is pretty cool.
HOWEVER, InDesign has the leg up in this case because of something important. You see, in InDesign, while guides are objects, they are "special" kinds of objects. And in InDesign, when you make selections, you can either select guides, or objects -- but not both. In fact, in InDesign, if you marquee select an area that contains both objects and guides, only the objects become selected. In this way, InDesign intelligently allows you to have unlocked guides that don't get in the way, yet can easily be repositioned at any time.
Illustrator CS3 suffers from a problem because guides aren't special objects -- they are objects. And so, if guides are unlocked, they become selected just as art does. The result is that while Illustrator CS3 makes it really easy to reposition guides, it's also really easy to constantly move and delete guides along with your artwork. In fact, you may find that one of the first things you do when using Illustrator CS3 is lock the guides so you don't keep accidentally selecting them.
If the Illustrator team wants to keep guides unlocked moving forward, I would recommend they adopt InDesign's logic for selecting guides as well. Otherwise, the guides just keep getting in the way.
An alternative solution is to create a new layer in your document -- and only add guides to that layer. In that way, it might be easier to just lock and unlock the entire layer (FreeHand anyone?).
Or here's another possible solution. Create your guides, and then group them. If you want to move individual guides without other objects getting in the way, double click on one of the guides to enter group isolation mode. Then only your guides are active in your document, and you can move them easily. Simply double click to exit the guide group and you're back to working.
Still, I like InDesign's implementation in this regard.