Design Matrix for Random effects

Hi all

I would like to obtain the design matrix for the random effects, without 
running (g)lmer first.

Could anyone help me do that ? For example, working with the sleepstudy 
dataset

sm1 <- lmer(Reaction ~ Days + (Days|Subject), data=sleepstudy)

sm1 at Zt is the transpose of the matrix I require, but I would like to 
obtain it without running lmer.

Thanks
Robert Long