The skateboard

2. Completely different
4. Close friends
6. A gymnasium, a place where you can go to work out
8. Admit that one has committed a crime or done something wrong
11. Someone who is obsessed with exercise and keeping himself or herself fit
13. The action of walking with difficulty, typically because of a damaged or stiff leg or foot
15. Of great or more than average height
17. When someone is doing something that creates a feeling of self-consciousness, shame, or awkwardness

1. A person who designs or builds rockets
3. An injury appearing as an area of discoloured skin on the body
5. The branch of science concerned with the nature and properties of matter and energy
7. A pole up which bean vines may climb
8. A prehistoric man who lived in caves
9. The sport or pastime of riding on a skateboard
10. To gain weight especially by becoming more muscular
12. Belonging to the same family
14. A person who is knowledgable about and obsessively interested in a particular subject, especially one that is technical or of specialist or niche interest
16. Being tall, thin and usually lose-jointed