G-d told Moses "...make a cover for the Ark."
The tablets housed in the Ark signify the union with G-d that we achieve by studying the Torah. The cover of the Ark signifies G-d's grace from above, which we require in order to maintain Divine consciousness at times -- even while uniting with Him through studying the Torah.
G-d grants us this assistance in virtue of our intrinsic connection to Him, which exists independent of the connection that we forge with Him through studying the Torah and observing the commandments.
This intrinsic bond is alluded to by the fact that word for "cover" (kaporet) is related to the word for "atonement" (kaparah). Atonement for sin is possible only when we invoke and evoke G-d's essential love for us, which overrides the deficiencies in our relationship to Him that we cause when we disobey the Torah's instructions.
Our constant opportunity to repair and renew our relationship with G-d (represented by the Cover of the Ark) transforms our study of the Torah (represented by the tablets within the Ark) from a purely intellectual pursuit to a springboard for spiritual growth.