A sundial shows the time by displaying the position of a shadow on a (usually) flat surface, which has markings that correspond to the hours.
Sundials can be horizontal, vertical, or in other orientations.
Types of Clocks
An hour glass , also known as a sandglass, sand timer, sand watch, sand clock, or egg timer, measures the passage of a few minutes to an hour of time.
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a harmonic oscillator, meaning it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates.
A pulsar clock is a clock which depends on counting radio pulses emitted by pulsars.