Production line comprising: - at least one assembling station, - a chain conveyor device comprising a chain for transporting a plurality of pallets along said production line, wherein each pallet is provided for transporting parts to be assembled, - motor means for moving said chain, - an electronic control system, - said motor means and said electronic control system being configured for causing said chain-transported pallets to proceed with a continuous movement through said at least one assembling station, said production line being characterized in that: - an implement is associated to said at least one assembling station, wherein said implement is guided on a support structure in such a way as to be freely movable along the transport direction of the pallets, whereby said implement can be used by an operator dedicated to the assembling station in order to execute manual assembly operations on the parts transported by each pallet, said implement thus being adapted to be pulled by the operator while the operator follows the pallet in its continuous movement through the assembling station, for executing said manual operations, - in association to each pallet, said chain is provided with a front hook unit and a rear hook unit which are longitudinally spaced from each other and adapted to engage the pallet for locating the pallet relative to said chain and for causing the pallet to advance along with the chain, - said rear hook unit being adapted to release the pallet when an obstacle prevents the pallet from proceeding along with the chain, said rear hook unit being also adapted to move, in this condition, to an optical beam interception position, in which a first interception element which is part of the rear hook unit intercepts a first optical beam emitted by a first optical sensor, - said electronic control system being programmed for generating a command signal when said first optical beam is intercepted by said first interception element. - at least one assembling station, - a chain conveyor device comprising a chain for transporting a plurality of pallets along said production line, wherein each pallet is provided for transporting parts to be assembled, - motor means for moving said chain, - an electronic control system, - said motor means and said electronic control system being configured for causing said chain-transported pallets to proceed with a continuous movement through said at least one assembling station, - an implement is associated to said at least one assembling station, wherein said implement is guided on a support structure in such a way as to be freely movable along the transport direction of the pallets, whereby said implement can be used by an operator dedicated to the assembling station in order to execute manual assembly operations on the parts transported by each pallet, said implement thus being adapted to be pulled by the operator while the operator follows the pallet in its continuous movement through the assembling station, for executing said manual operations, - in association to each pallet, said chain is provided with a front hook unit and a rear hook unit which are longitudinally spaced from each other and adapted to engage the pallet for locating the pallet relative to said chain and for causing the pallet to advance along with the chain, - said rear hook unit being adapted to release the pallet when an obstacle prevents the pallet from proceeding along with the chain, said rear hook unit being also adapted to move, in this condition, to an optical beam interception position, in which a first interception element which is part of the rear hook unit intercepts a first optical beam emitted by a first optical sensor, - said electronic control system being programmed for generating a command signal when said first optical beam is intercepted by said first interception element.