Here is as complete an explanation as you're likely to get anywhere.
https://space.stackexchange.com/questions/41958/apollo-command-module-heatshield-tube-what-was-it-forTl;dr—yes there were stainless steel bolts that passed through the ablative portion of the heat shield in three places. But to be pedantic, this connects the CM to the SM, not to the Saturn IV-B stage. "Tension tie" is functionally equivalent to "bolt" in this application, although it's still ambiguous whether it was cylindrical or not. It seems to be, but other commentators describe it as a "strap." The illustration labeled Figure 11 is the most helpful. The compression pad (not labeled) is tightened until it presses upward hard on the CM, putting the tension tie in, well, tension. This compression-tension strategy is very much like how bombs are attached to airplane wings. It keeps them from wiggling around.
At separation, the linear shaped charge cuts the tension tie, the CM end of which stays there and gets very, very hot during reentry. The portion of the heat shield around the compression pads and tension ties are composed differently, and there is thermal isolation on the CM side.
The video also gives a very informative close-up of the fluid and electrical connections that went around the heat shield and were guillotined apart at separation.