Learn Spanish (Latin America): El martillo con el que el hombre rompe el cristal no es auténtico. - The hammer the man breaks the glass with is not authentic.

In English, we often end a phrase with a preposition, like 'the hammer the man breaks the glass with'. In Spanish, a preposition cannot dangle at the end. It must come before the relative pronoun. So, you literally say 'the hammer with which the man breaks the glass'. Since martillo is masculine and singular, we use el que after the preposition con, giving us con el que.

Could I use con quien instead of con el que here?

No. The words quien and quienes are only used to refer to people ('who' or 'whom'). Because el martillo is an object, you must use el que.

What if the sentence was about a feminine noun, like la herramienta (the tool), instead of el martillo?

If the noun were feminine, you would change the relative pronoun to match its gender. Instead of con el que, you would say con la que to match the feminine noun (la herramienta con la que el hombre...).

Does el cristal mean 'crystal' here?