A few months back, I covered TwoUp and SizeUp, two utilities for managing windows on your Mac. TwoUp and SizeUp let you use keyboard shortcuts or a systemwide menu to arrange windows on the screen—for example, to place two (or three, or four) Finder windows next to each other to transfer files between them, to arrange several word-processing documents to compare their contents, or to position a BBEdit document next to your Web browser to preview your code.

The developer of TwoUp and SizeUp has since released another related utility, Cinch. Like TwoUp and SizeUp, Cinch makes it easy to resize windows to specific sizes and locations; however, Cinch limits your resizing and positioning options while making its functionality easier to access.

With Cinch installed, drag any window (via its title bar) to the left-hand side of the screen, and when your mouse cursor “bumps” against the edge, you’ll see an outline encompassing the left-hand half of your display. Release the mouse button and the window is resized to fill that outline. Drag another window to the right-hand edge of the screen and release and that window takes up the right half of the screen. By simply dragging the title bars of two windows against the edges of the screen (gotta love Fitt’s Law), you’ve perfectly split your screen between those windows. (When I first started using Cinch, I occasionally resized windows when I meant to just move them to the side, but it didn’t take long for me to get used to the “live” edges.)

You can use a similar trick to resize a window to fill your display: Just drag the window towards the top of the screen; once your cursor hits the top edge and you see the full-screen outline, release. Unlike OS X’s Zoom command, which acts a true full-screen zoom only in some apps, Cinch’s full-screen feature works with every window (well, almost every window; see below).

A welcome touch is that Cinch remembers each window’s original size (though not its position): Drag a window away from the side or top of the screen, and it immediately reverts to its former size.

If you’ve got multiple displays, one drawback is that you lose the “solid” boundary on the border between the two screens. To activate Cinch on that side, you need to position the cursor precisely at the edge of the screen until you see the Cinch outline appear. As a workaround, Irradiated Software recommends arranging your screens, using the Displays pane of System Preferences, so that they’re slightly offset; you would then drag a window into an offset corner to Cinch-resize it. (Of course, this approach would prevent you from using that corner to activate Expose, Dashboard, or the screen saver.)

Similarly, if you’re using OS X’s Spaces feature, and hold a window against the screen edge for too long, you’ll switch to the next space in that direction. The developer provides a tip for changing the Space-switch delay.

Finally, it’s worth noting that, like TwoUp and SizeUp, Cinch doesn’t work with some apps that don’t use standard Mac OS X windows; some windows resize but their contents don’t redraw properly, while other windows can’t be resized at all using Cinch. The Irradiated Software Website provides a list of known problem apps.

Those limitations aside, I’ve been enjoying using Cinch. I didn’t realize how often I want to place two windows side-by-side until Cinch made it so easy to do so.

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