Slacks are pants.

I read your post again and I'm not sure that is what you are looking for. Shorten slacks to describe a sewing machine? Maybe it refers to a part of the machine that hems pants.

As Sally says, slacks are pants or "trousers" as we say on this side of the "pond". Your question, however, is ambiguous. It could be an "imperative" directive for someone to shorten a pair of long slacks. It might also be a missspelling of an already pair of long slacks which have been cut down which now makes them "shortenED slacks". Hope this helps.

HI Dunia, look at this

Shorten Slacks

Failing this, type "shorten slacks" in quotation marks in google search and there are loads of sites.

Dunia, I'm pretty sure Sally is right here. Your phrase probably occurs in a context such as "With this machine you can perform many functions, such as shorten slacks, ..." When pants are sold, they are sometimes unhemmed, and have to be hemmed at home. Or, a hemmed pair of pants may just be too long for the wearer, and need to be shortened.

Thanks to all of you, if "slacks" means pants the meaning is quite clear, that is the sewing machine is able to hem pants.

Dunia said:

Thanks to all of you, if "slacks" means pants the meaning is quite clear, that is the sewing machine is able to hem pants.

Slacks are most often men's dress or semi-dress pants. (You sometimes hear someone say "women's slacks," but not very often.) Jeans would not be called slacks.

Shorten slacks is the name of a hem sewing machine. Just click on my "shorten slacks" link in my previous post.

Eddy said:

Shorten slacks is the name of a hem sewing machine. Just click on my "shorten slacks" link in my previous post.

The link was helpful. However, "shorten slacks" isn't the name of the machine. It's a description of what the machine can do. (And it makes sense. I've shortened slacks before, but I had to do it by hand, because my table-top sewing machine isn't suitable for that.)