If you were taught to put a 4x4 gauze pad on it, you are missing a crucial detail such as that you use PETROLEUM (jelly) gauze or to leave the (rare) plastic or foil wrapper on the gauze pad. Of course, you can't really tape to petroleum gauze so people use just the aluminized plastic wrapper or leave one side of the wrapper covering the pad and tape to the wrapper (do not do this with regular gauze pad and wrapper).
Regular gauze with tape on 3 sides of it makes no sense. Gauze is porus so you can't make a one way flapper (flutter) valve with it, which is the reason for taping three sides (or taping four sides but leaving one corner untaped. It is also the reason for using an occlusive dressing. Which can be tegaderm, cling wrap, aluminum foil (may not be flexible enough for flapper valve), aluminized mylar, glove, zip lock bag, or the plastic wrapper for other medical supplies (clean side towards patient).
Note that tyvek™ wrappers used to package and sterilize many medical devices are somewhat breathable and might not be sufficiently occlusive; they have small pores that keep water and germs out but allow water vapor to penetrate; this is a medical grade version of the same tyvek (spun bonded polyolefin) non-woven synthetic textile you see used in house wrap (construction vapor barrier), disposable coveralls, better floppy disk sleeves, and better quality mailing envelopes (the ones you can't tear), bibs for bike racers, and certain other waterproof "paper" applications.
If you have a sucking chest wound, you need to let air out but not back in again, to minimize pneumothorax.
Not surprisingly, the 3 side tape improvised flapper valve has rather dubious effectiveless, like many things we were taught in school.
An article in JEMS recommends use of an Asherman Chest Seal or a defibrilator pad (manually burped occasionally) instead of the usual flapper valve due to the slowness of application and tendancy for adhesive failure in the regular flapper valve.
http://www.jems.com/articles/print/.../treating-sucking-chest-wounds-and-other.html