Editoral vertical brackets

[Reuben Thomas]

How can I draw editorial brackets [ ] around some notes?

[I'd like to take this opportunity to thank everyone for putting up with a
tsunami of email over the past couple of days; thanks to all your help I'm
now starting to trundle along quite happily typesetting, and the
remaining few problems I'm collecting together for later.]

-- 
http://www.mupsych.org/~rrt/
Careful Cyclists Approaching From Right (Anon)