How could u tell if ur doing push ups wrong, or if ur body issint straight during push ups?

A long time ago when we had Big Boy rifles in the Army, the Sgt. laid a rifle on our back and if the end of the stock and barrel tip didn't touch our body, we were not doing a push up correctly.

You can probably substitute a broom for a rifle. Both ends and the middle have to touch your body while you do push ups.

Just record yourself with your phone.

-Arms must be placed with the width of your shoulders, so they shouldn't be extending outwards from your shoulders.
-You must push down until your arms make a 90 degree angle.
-Your toes should be touching the ground not your feet.
-Body should be parallel to the ground. You shouldn't be pushing your butt down or too high. You'll know when you're straight with the ground. Your back should be comfortable.