What is lintel? how many years ago was the pyramid of cheops built?

A lintel is a horizontal support of timber, stone, concrete, or steel across the top of a door or window.  

The Pyramid of Cheops was built 4,500 years ago.

A horizontal support of timber stone concrete or steal going across dors or windows and the pyramid of cheops was buit 4,500 years a go

the printing press made a huge difference in the arts and crafts movement.