I was asked to create a K'nex roller coaster for a youth group's hot dog fundraising stand, and this is what I built them.
It fascinated the children and adults alike... and they sold out.
Most common question: "How long did that take to create?" (About a month)
Children could ride the roller coaster for $5 - but had to be under 2cm tall to ride.
Assembled at home over a month.
A mount created for all four corners to connect the structure to.
Pulled apart into 6 main sections for transport to fit in a van.
(the lift hill even needed the top 3rd taken off.)