Extending / shortening a clip and locking with another clip's edge

[Charles5FEF]

I'm sorry for the newbie question but I don't know what I did or pressed wrong. Before, whenever I extended or shortened a video or audio clip, it would lock on to the other clips nearest to it so that they're aligned. Now for some reason, it won't lock with the other clips, so it's hard to make sure the clips are all aligned. Did I press something wrong, and what I can I do to bring it back?

[John V Knowles · Accepted solution]

Check to see if the little MAGNET icon in the timeline panel is on (blue). That's the snapping control you're looking for. 

[Charles5FEF]

Brilliant! Must have pressed it by mistake. Thanks, you're a life saver.

[Michael Grenadier]

there's also a shortcut key that you might have pressed by accident.  It's in the sequence menu "snap in timeline"

Not sure if it's the same everywhere but on my system it's "n"