Lowes offers Simpson Strong-Tie ZMAX Galvanized Steel Rail Bracket for $0.93. Free shipping on orders over $35. 

Product Description:
The FB is designed for connecting fence posts to rails. The simple design of this fence rail bracket provides strong connections without the need for toe nails or screws. The versatility of the FB makes planning and building fences, deck/porch railings and louvers fast and easy.

• Preinstallation of brackets allows rails to slide into place easily
• Eliminates need for toe nails or screws
• Nominal member size: 2x4
• Made from 20-gauge steel
• ZMAX galvanization offers extra corrosion resistance for exterior and treated-wood applications
• Holes are sized for 0.131-in x 1-1/2-in nails, 0.131-in x 2-1/2-in nails or #9 x 1-1/2-in Strong-Drive SD Connector screws into the supporting member