what does double threaded mean?

[missdnm]

i want to buy a polarizer filter for my camera but i want to be able to attach my wide angle lens on to it...if its double threaded does that mean i can do this?

 

[will965]

It means that the filter has 2 threads . One to screw the filter on to the end of your lens and on the other side the thread allows another filter or lens hood etc. to screw onto the filter. (dunno if any of that makes sense)