Rashi on Terumah 26:1

English: ואת המשכן תעשה עשר יריעת MOREOVER THOU SHALT MAKE THE DWELLING OF TEN CURTAINS — that they should serve it as a roof and at the same time as wall-coverings for the outside of the boards; — for the curtains hung behind them so as to cover them. שש משזר ותכלת וארגמן ותלעת שני OF FINE TWINED LINEN AND BLUE PURPLE, AND RED PURPLE, AND CRIMSON — Thus there were four different materials in every thread, one of linen and three of wool, each of the strands of which a thread was composed being sixfold (the word is taken here in the double sense of שש “linen” and of שש “six”). Consequently the four materials intertwined into one thread gave a twenty-four-fold thread (Yoma 71b; Baraita DeMelekhet HaMishkan ch. 2). כרבים מעשה חשב WITH CHERUBIM, THE WORK OF AN ARTIST — Cherubim were figured on them (on