If your 'fridge has a black grill on the back, it probably does not have refrigerant lines in the sides. That's no guarantee.
Depending upon the age of the 'fridge, you may be able to google its brand, model, serial # and get a description of where the lines are located.
In my case I put my faucets on the side. My 'fridge did have the grill on the back and I was able to get a description of the line location.
However, I still used a holesaw to cut a small hole in the plastic interior, used a small screwdriver to probe around in the foam insulation between the plastic and the exterior metal skin to verify that there were no lines in the area.
I needed five holes for faucets and one for the CO2 line and this added an extra 30 minutes to the process.
I just didn't want to take a chance in turning my 'fridge into a very large and expensive paperweight!