It's called JBmod and this probably isn't a repost of anything unless I missed something. Basically, you download this map:
http://www.kieranf-j.pwp.blueyonder...locks_Final.rar
The notepad doc inside tells you where to install and such,
and most of all, download the mod:
http://www.kieranf-j.pwp.blueyonder.co.uk/jbmodv05.zip
once again, a notepad doc tells you what to do.
After you load up JBmod with the given instructions, go into console, type map buildingblocks_final to load up the building blocks map. what it esentially is is a blank map with a bunch of terminals that spawn all sorts of different items. That is all that buildingblocks is. JBmod comes into effect when you type "impulse 101" into the console to get all the weapons. A weapon is added called the phys gun, take it out, right click adds a sticky blob to one surface (object from the spawn terminals or even the ground or a wall), add another blob to another object, and click with the left mouse to drag the object to stick the too sticky blobs together. you can form very... interesting things, such as these creations people have made:
http://www.kieranf-j.pwp.blueyonder.co.uk/tribute.avi
http://www.kieranf-j.pwp.blueyonder.co.uk/.../challenger.avi
It takes some practice to get anything good looking to actually work, but when you do, it's pretty sweet. So far I've only made as much as like... an airplane, which was hard to do.
but be warned, the mod is still a little unstable and does crash sometimes. Have fun, post any cool results perhaps. Further questions and I suppose I'll be able to help, but not today, or tomorrow, but maybe after christmas.