This Seeking Tech guide will show you how to get the Don’t Touch the Sides trophy and achievement in Metal Gear Solid Delta: Snake Eater.
This will unlock when you “use a knife to remove a bullet.”
The best opportunity to do so is during the fight with Volgin or The Boss. Both opponents will eventually shoot you with bullets that get lodged into your body.
Once you see red on your health bar, head to the Cure menu. You then need to use the knife, disinfect, styptic and bandage to heal yourself in order to get this trophy/achievement.
You can find a video walkthrough below: