Apex (diacritic)
The apex is often thought to be the opposite of another ancient Latin diacritic, the sicilicus, which is said to have been used above consonants to show that they should be pronounced as doubles. However, in his article Apex and Sicilicus, Revilo P. Oliver says that they are the same sign, a geminationis nota. This was used over any letter to show that the letter should be read twice.