How to make a digital pin act as ground?

Projects General Guidance
1

My Hc-sr04 arrived today and I'm connecting it using a bread board. It's a bit difficult. I want to mount the ping sensor directly on the arduino. But I don't know how to make a pin act as ground. Am I supposed to make it as an input? Or set it as an output and set it to low?

Thanks!

2

"act as ground" is slightly non-sequitor. First, there are actual ground pins on the
Arduino board. Secondly, if what you need is an "active-low" signal (5V --> 0V),
then you do what's stated in your last sentence.