Ever wonder what all those little threaded bosses on your bike frame are for—beyond just holding water bottles? In this quick guide, we’ll demystify braze-ons and show you how to use them to carry bottles, cargo cages, pumps, locks, bags, even lights. We’ll also cover creative workarounds when you don’t have braze-ons (like universal support bolts), and discuss whether it’s possible to over-populate your frame with mounts. By the end, you’ll know exactly how to equip your bike for any adventure, big or small. What are Braze-Ons? Braze-ons (also called eyelets) are small threaded bosses on your bicycle’s frame or fork, designed to let you bolt on accessories securely. Most modern bikes, including commuter bikes, gravel bikes, and touring bikes from manufacturers like Priority Bicycles, include at least two pairs of braze-ons in the main triangle for water bottles, plus more on the fork or seat stays. For examples of bikes with multiple braze-ons, see: Priority Gemini Priority Apollo Gravel Priority 600ADX Priority 600HXT Priority Bruzer These bikes feature numerous mounting points for all kinds of adventures. Things You Can Bolt On Here’s a breakdown of common and creative uses for braze-ons: Water Bottle CagesThe most traditional use. Most frames accommodate at least two standard bottle cages. RacksRear racks can mount to braze-ons on the dropouts and seat stays for hauling panniers or groceries. Many Priority Bicycles bikes come with optional racks or can fit third-party ones. FendersEssential for wet-weather commuting, fenders mount to eyelets near the dropouts and fork. Pumps and LocksSome frame pumps and U-lock holders bolt directly into standard bottle bosses. Bags and StorageBolt-on frame bags use eyelets to avoid straps. Pro Tips Always check the thread pitch and size (usually M5 x 0.8) before attaching. Don’t over-tighten! A torque wrench helps prevent damage. Use stainless hardware if your bolts are exposed to wet conditions.