"maternity belt"

Hi, All. I just had a quick question for those in the family who are or have ever been pregnant. I have seen something called a maternity belt (I think), that is basically support for your lower back. It's like an elastic belt that goes under your belly to take some of the weight off of your back. Has anyone used one? Do they help? (Husbands, feel free to relay the question to your wife or give any input you might have.) My lower back doesn't feel good some days (especially when I over use it) and I've considered trying one of the belt thingies.