I have created isometric cubes for an experiment but I’m not sure if they are tile-able:

/‾‾ no. 1 horizontal cube
/__/

__ no. 2 vertical cube
|‾–‾|
|_ _|
‾‾

— no. 3 vertical cube 2
|-__-|
|_ _|
‾‾

I want it to have the diagonal edges like no. 1 but be vertical, not horizontal like no. 2 & 3.