Below is the 19th drawing in the set of 21 for this lawnmower powered wooden go-kart.
There are now a large number of different types of brakes on bicycles from disc brakes to calliper brakes etc. This drawing shows how an old type of bicycle brake can be used and adpated to suit this wooden go-kart. The spoked wheels for this kart were off a small childrens bicycle. Therefore the brakes off the same bicycle worked perfectly. If you were using a solid wheel or different type of wheel, then you would have to adapt and improvise by attaching a disc/plate to the rear axle and to operate the brakes on this.
It would be possible to fit brakes on the front wheels, and this would give much better braking performance, however this would require some extra work.
Make sure to test the brakes and that they will be sufficient to stop the kart. Its no use putting brakes onto a go-kart if they won't work. Bolts are used to attach the brakes to the wooden cross beam, making sure that everything will hold when stopping the kart quickly.