How do you build underground belts?

[Mastro2k]

I have the "underground belt" which visually looks like it's going into the ground but how do I extend that underground?

[NimrodAbsolution⁧⁧98]

you place the first down then within 4 blocks of the direction the first is placing you place the second

[Mastro2k]

Aww thank you. I didn't realize you could only go 4 out like that. Thought maybe there was some underground view.

[bobSheep]

There's a mod that allowed for 30 tile underground belts. I just used it for the first time but imho makes the game waaay to easy like that