It is not uncommon for males to be unaware of the term "frenulum" even though the area is a very sensitive one. The picture below shows where and what the frenulum is. In this example, this frenulum is short and prevents the foreskin from being pulled down to become smooth on the shaft. After circumcision, if the shaft skin becomes tight during erection, the frenulum would likely tug down on the glans, preventing it from standing up and instead having a slant.
There are ways to releive this slight problems without removing the frenulum in its entirety,
and there is also the possibility of removing it entirely.
One need not be circumcised to fix a short/tight frenulum (this condition is called frenulum breve.