Straplocks From Grolsch Beer! This good tip comes from 300guitars subscriber Michael Epstein. This is a great tip for guys who like Grolsch beer. It seems that if you take the red colored rubber washer from the bottle top and slip it over your strap button you have an instant straplock! They are free when you buy the beer and easy to replace. So if you like Grolsch beer drink up and get free straplocks! Check out MORE awesome Guitar Tips and Tricks from Billy Penn!