In Ultimate Obstacle Race Training, we went into detail about all the different walls you will face at most obstacle races and mud runs. Some are larger than others (Tough Mudder's Everest for example) others are made from interesting materials (like Hadrian's Wall at Victory Quest, made from old tires lashed together) but for the most part walls are exactly a you'd expect: A barrier between you and the rest of the course that you need to scale – by any means necessary – to continue on your quest to finish the event.
To help you in your training, we've designed a DIY wall you can build in your own backyard. You can find the guide here. Enjoy!