roll the edit back or forward “rolling” out new footage and taking up old footage to keep everything in sync. This is a roll edit. A single roller 
trim only trims footage on the selected side, taking up or adding new frames, and can throw off sync depending on how the sync locks are set. This is a ripple edit. Final Cut Pro ‘s Trim Edit window works much in the same way when performing ripple and rolls edits from within the Trim Edit window but without the elegance of Avid. When you want direct timeline manipulation of a ripple or roll edit, it’s very different. A bit more on that later. Trying to explain how trimming works is not the easiest thing in the world. If you don’t use trimming on a regular basis then the best way to learn how it works is to just play with the tools. You’ll discover that with a couple of key strokes you can fine tune an edit with speed and precision you might have never though possible… much more so in Avid, but also in FCP.
or Slide tool 
in the tool palette, and click and drag the segment in the timeline you want to edit. You are presented with a "2 up" view that shows incoming and outgoing frames.
While a FCP slip and/or slide edit is very simple to perform in its selection and execution, its power is somewhat limited especially compared to power and elegance available in Avid’s trim mode. The ability to use they keyboard and regular playback and scrubbing methods while executing a trim really can't be explained, it must be experienced to understand how useful it can be. I can sum up the slip/slide editing comparison quite simply: Avid’s implementation is a bit more difficult to execute, but when it is understood, FCP’s tools cannot match its power and usability. I think this goes back to one of the most fundamental differences between the two applications. FCP is geared much more toward mouse driven timeline manipulation than Avid has been or ever will be. Avid is much more about speed and efficiency.
FCP's trim preferences. I've changed my Multi-Frame to 10 frames.
There are settings under the User Preferences > Editing tab that determine how the trim tool operates. Settings such as Trim with Sequence Audio and Trim with Edit Selection Audio (Mute Others) are settings that are really not needed (not to mention confusing to use). It seems to me that these settings are attempting to make the monitoring of audio trims quicker and easier but they just complicate matters. I have read the manual's description of these trim preferences but it just doesn't seem to work at the manual indicates. The audio monitoring depends on item linking and that just makes trimming way more complicated than it has to be. Avid’s approach is that when you trim you monitor all sequence audio that is currently active. It seems like a no-brainer. If you don't want to monitor audio, mute the tracks you don't want to hear. This is how Avid operates. Monitoring and trimming in FCP is very dependent on how you have Linked Selection toggled. And one of the most frustrating things in FCP is that when you select audio only to trim, FCP does not show you the video in the Trim Edit window. I may not want to trim video but I would always want to see the footage rather that staring at speaker icons.
A couple of versions ago FCP added a feature called Dynamic Trimming 
(which can be toggled on or off) that allows the direct playback of an edit via JKL shuttling while in trim mode. That was a welcome addition and made trimming in FCP much more useable than it had been. This is something that Avid has had all along.
in the tool palette and click and drag the edit to perform the trim. A roll edit that changes the IN and OUT point of an edit and rolls the edit forward or backward requires the selection of the Roll Tool 
.While selecting the tool (either via clicking in the tool palette or using a keyboard selection) is an extra step but you do get visual feedback while dragging in the timeline. You can use dynamic trimming to perform a ripple edit (or single roller as Avid calls it) within the trim tool by clicking either the incoming or outgoing frames in the trim tool window and dynamically playing the edit via the JKL keys or using the Multi-Frame trim buttons but you don't get any kind of visual feedback in the timeline. In Avid, performing a ripple edit (or single-roller trim as it’s called) is as simple as entering trim mode, clicking the incoming or outgoing frame in the Composer window, depending on which side you want to edit, and playing the edit out with playback tools. As you trim, Avid shows what is happening directly in the timeline with a little indicator that moves forward (or backward) from the edit to visually show you what is happening. By using keyboard shortcuts you can enter trim mode with one keystroke, choose which side of the edit to trim and play out the trim with the play button. It is very fast and efficient.
Normally at this point I would link back to the blog entry and talk about which application that I personally thought was better for the particular item compared but I think it's obvious from the article that I feel the Avid's trimming is light years ahead of Final Cut Pro. FCP is on the right track as mechanically it works very much the same way as Avid but it's the refinement that is far behind what Avid has been offering for years. We're due for a rather large FCP upgrade so we'll see what happens then.
