Eragon wants to make a saddle for Saphira with the leather hides he stole from Gedric, Carvahall's tanner. Brom tells Eragon that the Riders made two kinds of saddles. One was like a horse's saddle, hard and molded. The second was just a layer of leather between the Rider and his/her dragon. They were good for speed and flexibility. Brom makes one made for speed for Eragon, because the one like a horse's saddle takes time and tools, which they did not have.
After the saddle is made, they decide to go to Therinsford the next day to buy horses.