This is an indication that the firing pin is un-cocked. In order to install the bolt into the receiver you first re-cock the firing pin. To re-cock the firing pin you must rotate the bolt shroud at the rear of the bolt body clockwise. Sako rifles are provided with a tool for this purpose, Tikka bolt shrouds must be rotated by hand. It will take some strength or force to rotate the bolt shroud as you are cocking the spring tensioned firing pin as you turn this part. This procedure is similar to the instructions outlined in the rifle owners manual referring to the removal of the firing pin, . The difference is that you only rotate the bolt shroud to the first notch in the bolt body instead of turning it until it stops as per the removal instructions.