The teams really do not find out what they have to build until that morning, on camera. The producer has been very suprised at what the teams made sometimes. By carefully seeding the yard, they make it possible to have challenges that would be impossible otherwise. If you want remote controlled flight, you have to include the radios, there is no way a team could make a legal system if you don't. To show steam engines, you have to supply a boiler and all the fittings, as improvising a boiler is simply not legal to do.
Ingenuity is still the most important thing the producers put in that yard.
The most used tool is still the brains of the team members.