Subassembly for securing a boot to a sliding device, comprising: - a rear retaining device for the boot, comprising: ∘ a body, ∘ at least one holding element designed to engage with the heel of the boot in order to retain the heel, the holding element being able to move with respect to the body, - a brake device comprising: ∘ a stop element that is able to move between an active position, in which the stop element is configured so as to brake the motion of the sliding board, and an inactive position, in which the stop element is configured so as not to brake the motion of the sliding board, ∘ a locking mechanism comprising: ▪ a locking member that is able to move between a locking position, in which the locking member is able to engage with the stop element so as to hold the stop element in its inactive position, and a free position, in which the locking member is not able to engage with the stop element, ▪ an actuator by means of which the locking member can be made to tip from its locking position into its free position, characterized in that the actuator is positioned relative to the body of the rear retaining device such that it can be activated by the boot and/or the holding element when the heel of the boot engages with the holding element. - a rear retaining device for the boot, comprising: ∘ a body, ∘ at least one holding element designed to engage with the heel of the boot in order to retain the heel, the holding element being able to move with respect to the body, ∘ a body, ∘ at least one holding element designed to engage with the heel of the boot in order to retain the heel, the holding element being able to move with respect to the body, - a brake device comprising: ∘ a stop element that is able to move between an active position, in which the stop element is configured so as to brake the motion of the sliding board, and an inactive position, in which the stop element is configured so as not to brake the motion of the sliding board, ∘ a locking mechanism comprising: ▪ a locking member that is able to move between a locking position, in which the locking member is able to engage with the stop element so as to hold the stop element in its inactive position, and a free position, in which the locking member is not able to engage with the stop element, ▪ an actuator by means of which the locking member can be made to tip from its locking position into its free position, ∘ a stop element that is able to move between an active position, in which the stop element is configured so as to brake the motion of the sliding board, and an inactive position, in which the stop element is configured so as not to brake the motion of the sliding board, ∘ a locking mechanism comprising: ▪ a locking member that is able to move between a locking position, in which the locking member is able to engage with the stop element so as to hold the stop element in its inactive position, and a free position, in which the locking member is not able to engage with the stop element, ▪ an actuator by means of which the locking member can be made to tip from its locking position into its free position, ▪ a locking member that is able to move between a locking position, in which the locking member is able to engage with the stop element so as to hold the stop element in its inactive position, and a free position, in which the locking member is not able to engage with the stop element, ▪ an actuator by means of which the locking member can be made to tip from its locking position into its free position,