For an electric guitarist, bassist or keyboardist, an amplifier is second only to the instrument itself on your list of essentials. You amp goes with you to every gig, so it's always on the move. That's what makes frames, casters, legs and corners so important—their job is to help protect and position your amp as you go from one venue to the next. Whether you're looking for an add-on for your amplifier or to replace one of these parts, this is the section you're looking for.
Tilt-back legs are a useful accessory to help make your amp more of a multi-purpose device. You can mount these on a combo amplifier to tilt it, projecting the sound up to your ears instead of muddled along the floor. In that position, the amp can be used as a monitor when you're on stage, or help you hear more clearly when you're practicing or jamming at home.
On the road, one of the most useful additions you can make to an amplifier is a set of casters. These small wheels are a must for very large combo amps and speaker cabinets, allowing you to roll them easily across the stage when setting up or tearing down a gig. These casters can be added to cabinets that did not originally have any, and they're also great replacements if the stock casters on your amp are starting to wear out. For a smaller amp or cabinet where casters would be a bit much, you've got the option of mounting metal glides. They'll do the same job of protecting the bottom of the amp and making it easier to move, but without taking up as much space.
Corner caps are yet another amplifier essential. It could be that you're replacing stock plastic corners with metal ones to give your amp a premium or vintage look, or maybe you're restoring an old amp and need some authentic-looking caps. When browsing amp corners, keep in mind that they're usually packaged in sets of four—so you'll need two sets if you want to replace all eight corner caps on the cabinet.
Frames, casters, legs and corners are all things to think about for the frequently-traveling amplifier. These are great accessories for upgrading an amp that might not have had them before, as well as for making replacements. Your amp is one of the most important things you take on tour, so it's definitely worth the effort to keep it in good shape.