Merge / join edges

 From:  blindfoldjump
7216.1 
Hey there

My first post here, Im currently still using the trial version of Moi. Seriously considering this product, everything is great so far.

However Im trying to figure out how to join two edges together and collapse part of the object in the process so to speak.
If anyone is familiar with with Modo, you would just select two edges on a box for example and then go to Edge->Join (or 'Join average') for this to happen.
Essentially make a triangle from a box.

Any help appreaciated