two-by four over the head

[espejo_negro]

Hello,

I do not understand the meaning of the expression "two-by four over the head"
The context is "Holly Anderson's birthday surprise turned out to be a two-by four over the head."
I would translate it as "La fiesta sorpresa de cumpleaños de Holly Anderson resultó ser un fracaso"

Thank you in advance.

 

[Kindred]

(n): a timber measuring (slightly under) 2 inches by 4 inches in cross section

Una posible traducción: "un ladrillazo en la cabeza"

 

[espejo_negro]

Muchas gracias Kindred. Ya me queda más claro el significado de la expresión.

 

[TurbidTongue]

That metaphor is amazing! It made me laugh. Anyway, two-by-four is un madero, como los que se usan en la construcción de casas en los EEUU.
So, the comparison is that this surprise party was ¡tan agradable como un golpe de madero en la cabeza!

http://en.wikipedia.org/wiki/Dimensional_lumber#Dimensional_lumber