Znap is a Lego theme that was produced from 1998-1999. It is similar to K'nex and can also be used to build objects in a frame-like way. The plastic it is made of is slightly flexible yet strong. The back page of some instructions (found on Peeron) feature a small boy sitting inside a large Formula One racing car made from Znap.
Bridges and structures using Znap are often integrated into train layouts at shows. One challenge of doing so is that different parts came in different colors, and certain key connector parts were available only in strange colors, like purple, making uniform color bridges difficult to construct.