Martin Rychtařík - muzikant ze severu Čech 

It is called "fully erect" when the penis is fully inflated with blood, which makes it bigger and stiffer. The penis gets hard, straight, and bigger when the erection is full. It's also possible for the glans (tip) of the penis to stand out more. Men usually get a full erection when they are sexually aroused or stimulated, but erections can happen on their own, especially at night (called nighttime erections).

Different people may have different experiences, but one sign of a fully erect penis is a big increase in length and width compared to when it is limp. It is important to remember that erections can vary in size, shape, and look. The level of excitement, warmth, and general health can also affect the erection. If you are worried about your sexual health or are having problems that won't go away, you should talk to a doctor or nurse.