Yes. Urban planter boxes that attach directly to railings are widely available. They are usually sold as railing planters, balcony railing planters, or over-the-rail planters. Most use one of four attachment methods: saddle-style boxes that hook over the top rail, clamp-on brackets that grip the rail, hook-on metal frames that hang from the rail, and modular systems with adjustable brackets. Some are designed for specific railings, such as square metal, round tube, glass, or wooden deck rails.
For urban balconies and small courtyards, these planters are popular because they save floor space and add greenery at eye level. Choose a model that matches your railing shape and width. Check the railing's load capacity, because wet soil and mature plants can be surprisingly heavy. Lightweight potting mix, plastic or fabric liners, and drought-tolerant herbs or flowers reduce weight. If you rent, look for removable, no-drill clamp-on planters. If you have a glass railing, avoid direct metal clamps that can scratch or stress the glass; use padded hooks or a freestanding alternative instead.
Installation is simple: measure the rail, clean it, add rubber pads to prevent scratches, and tighten clamps evenly. Avoid blocking fire escapes, doors, or emergency exits. Water carefully to prevent drips onto neighbors below. With the right railing planter boxes, you can create a productive urban garden in minutes.