How to readily identify low & high pressure lines in split AC system for hooking up the gages?

I'm trying to measure the pressure of the refrigerant in the 1.5 ton split ac system in connection with a suspected leak. Of the two 1/4" ports at the compressor which is low ? One port is connected to a 7/16" dia exposed copper tubing. The other is connected to an insulated 1" dia copper tubing. I found no web site that clearly describes the physical looks of these lines associating with their respective names. I believe there are other terms used for low pressure line such as suction line and any other synonyms without mentioning means of physically identifying. May be basic but essential for DIY projects. Thanks a lot for your ASAP response.