You can get an appreciation for how vexing and commonplace the problem of ruffled, untucked shirts is in the military by the variety of products
FLEX-BELT HIDDEN TAILOR SHIRT STAY
USMC UNIFORM ACCESSORIES
ZipSeam- Instantly Tailor Your Clothes by SiDi Huang — Kickstarter
NAVY UNIFORM ACCESSORIES
ARMY UNIFORM ACCESSORIES
FlexRS is a proprietary low-profile stretch ripstop material which looks like a regular shirt, but performs like a BDU. Our FlexRS ArmorSkin Base Shirt also features built-in anti-odor treatment, durable water repellent coating, and combines with our FlexRS ArmorSkin XP to make the ultimate comfort uniform.
Blauer 8361 FlexRS Base Long Sleeve Shirt
USCG UNIFORM ACCESSORIES
MERCHANT MARINE ACCESSORIES
Hidden Tailor
Helps create the tailored look for your clothes., The Hidden Tailor Ultimate Belt by Flex- Belt is designed to be worn over the shirt tail, inside
Hidden Tailor Ultimate Belt
Gary's Anatomy
Galls Flexible Waist Belt
USCG UNIFORM ACCESSORIES