The practice of replacing the default Android operating system of a device, present in read-only memory (ROM), with a modified version of the OS or a completely different OS is called "ROM flashing". The procedure is generally not supported by device manufacturers, and requires advanced knowledge of OS mechanics. However, recent years have brought many more manufacturers, such as LG,[4] Motorola,[5] OnePlus,[6] Google[7] (but not on devices sold by Verizon), and Sony[8] allowing customers to unlock the bootloader, bypassing secure boot, without the need for exploits.