You gain a +1 bonus to attack and damage while wielding this magical weapon.
This rapier first appears to be a plain, solid metal bar measuring approximately 6 inches long. The bar has a hidden button which can be found with a DC 20 Intelligence (Investigation) check.
Pressing the button activates springs and gears hidden inside the bar that unsheath the weapon, causing a retractable blade to spring forth from the top, a small pommel to emerge from the bottom, and curved metal to extend from the sides creating a simple ringed hilt around the wielder's hand.
Pressing the button again sheaths the weapon, returning it to its original appearance as a plain, solid metal bar.
Proficiency with a rapier allows you to add your proficiency bonus to the attack roll for any attack you make with it.