Hello! There is a guide for HealthKit Clip (HKC)!

There is a 5 types of HKC - Through noncollision object, Through tilted object, Through grid, Through doors and with Supercharged GravityGun

Base - This trick can be used only with 2 players, 1 player clips 2 player through any object

Through noncollision object - Lets take the d1_canals_01 map as an example. Player 1 hold down W and press "kill" bind (You can find binds in "How to Setup game" guide), by doing so his dead body will pass through noncollision object. Player 2 go close up to object and revive Player 1. Its easy.

Through tilted object - It's all the same, except Player 2 needs to little push Player 2's dead body

Through grid - Player 2 needs to push Player 1's body, until his body passes through grid

Through doors - Everything is the same as with "Through grid", only you needs to make the body look out of the door a little and revive at that "little"

with Supercharged GravityGun - This method is more random than other 4 methods, but this method needed in HL2EP1. Player 2 just needs to grab Player 1's dead body with Gravity Gun and push it to object, until its passed through object

Additionally - I recommend you to read Unstuck command guide, because its really makes HKC easier

Thanks for help with guide to @DyorinHikan