I made two boxes, one large one for our kitchen window that has a mixed variety of nasturtiums growing in it. The other box is a bit narrower - sized more appropriately for the smaller adjacent window. That box is growing a climbing plant called Asarina Scandens "Joan Lorraine" with purple flowers that's known to be a good climber. It's already starting to creep up the bars and give us a bit more 'natural' privacy on our bathroom window.
This project is very easy and can be completed in a matter of hours with very affordable materials.
Step 1: Bang on Steel
Make a 90 degree bend around 2" in from one end. Expose another inch or two of steel in the vice and make another 90 degree bend.
The hook is now formed. Repeat for all lengths of steel.
Step 2: Drill Holes
Use a lubricant (bike chain lube works just fine) while drilling.
Remember to wear eye protection to protect yourself from the little bits that may fly off the drill bit.