A printer, comprising: a fluid ejection device (100; 520, 522; 600) having a set of coding elements (102; 524, 528, 530, 532; 604, 606, 608), each coding element (102; 524, 528, 530, 532; 604, 606, 608) being movable between an initial position (Pi) and a coded position (Pc), wherein each of the coding elements (100; 520, 522; 600) comprises a hook portion and a support portion that correspond to end portions of the coding elements (102; 524, 528, 530, 532; 604, 606, 608), wherein each hook portion and the corresponding support portion are connected by a connection portion; and a first slot and a second slot each configured to receive the fluid ejection device (100; 520, 522; 600), the first slot having a first lockout unit (508, 800) and the second slot having a second lockout unit (510, 802), each lockout unit (508, 510, 800, 802) configured to mechanically engage with the set of coding elements (102; 524, 528, 530, 532; 604, 606, 608), wherein the first lockout unit (508, 800) has a pushing member configured to push one of the coding elements (102; 524, 528, 530, 532; 604, 606, 608) into the coded position (Pc) and the second lockout unit (510, 802) has another pushing member configured to push another one of the coding elements (102; 524, 528, 530, 532; 604, 606, 608) into the coded position (Pc); wherein the fluid ejection device (100; 520, 522; 600) comprises a trap element (104; 526, 534; 610) configured to trap one or a plurality of other coding elements (102; 524, 528, 530, 532; 604, 606, 608) in the initial position (Pi) when the one of the coding elements (102; 524, 528, 530, 532; 604, 606, 608) is moved from the initial position (Pi) to the coded position (Pc). a fluid ejection device (100; 520, 522; 600) having a set of coding elements (102; 524, 528, 530, 532; 604, 606, 608), each coding element (102; 524, 528, 530, 532; 604, 606, 608) being movable between an initial position (Pi) and a coded position (Pc), wherein each of the coding elements (100; 520, 522; 600) comprises a hook portion and a support portion that correspond to end portions of the coding elements (102; 524, 528, 530, 532; 604, 606, 608), wherein each hook portion and the corresponding support portion are connected by a connection portion; and a first slot and a second slot each configured to receive the fluid ejection device (100; 520, 522; 600), the first slot having a first lockout unit (508, 800) and the second slot having a second lockout unit (510, 802), each lockout unit (508, 510, 800, 802) configured to mechanically engage with the set of coding elements (102; 524, 528, 530, 532; 604, 606, 608), wherein the first lockout unit (508, 800) has a pushing member configured to push one of the coding elements (102; 524, 528, 530, 532; 604, 606, 608) into the coded position (Pc) and the second lockout unit (510, 802) has another pushing member configured to push another one of the coding elements (102; 524, 528, 530, 532; 604, 606, 608) into the coded position (Pc); wherein the fluid ejection device (100; 520, 522; 600) comprises a trap element (104; 526, 534; 610) configured to trap one or a plurality of other coding elements (102; 524, 528, 530, 532; 604, 606, 608) in the initial position (Pi) when the one of the coding elements (102; 524, 528, 530, 532; 604, 606, 608) is moved from the initial position (Pi) to the coded position (Pc).