After switching the sights on my Glock 17 and finding no problem chucking the slide in a wood lined vise and tapping the rear sight into position with a mallet and wooden dowel, I thought a rear sight tool would be far more convenient if I want to make an adjustment at the range. But... For something I'd use so rarely, they seem pretty expensive.
So I designed one and printed it on my 3D printer. Being mainly plastic, I doubt it would hold up to as much use as an armorer would need, but since I only anticipate ever using it a handful of times and it's been effective to easily nudge the position of the rear sight, it's working for me.
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If there are other users with 3D printers that would like the files to print their own, I've uploaded it to Thingiverse:
http://www.thingiverse.com/thing:33587