garrys mod entity collision detection?

garrys mod entity collision detection?

Is their a way to get the entity that another touches/collide with? eg. I
throw a can(known prop, prop A) at a door(unknown prop, prop B) and
retrieve the entity object and the point where they first touched? (i'm
trying to make a harpoon for flood mod using hydraulics with a stress
limit and i'm new to lua ) any help? i am intending to use,
function standing on()
local trground = util.TraceLine( util.GetPlayerTrace( player.GetByID(X),
Vector( 0,0,-1 ) ) )
if IsValid( trground.Entity ) then
return trground.Entity
else
return false
end
end