Medium placement unit, transport device, and printing device

A medium placement unit comprising:

• a placement surface on which a medium is placed, and
• a restriction section that is movable relative to the placement surface in both a first direction, in which the restriction section approaches the medium placed on the placement surface, and in a second direction opposite to the first direction, and that restricts movement of the medium placed on the placement surface by engaging with the placement surface, wherein
• the restriction section
• includes a first portion and a second portion, and
• is engageable with the placement surface via at least one of the first portion and the second portion,
• the placement surface is provided with a plurality of third portions arranged in parallel with the first direction and a fourth portion,
• the first portion
• is engageable with each of the plurality of third portions, and
• when engaged with a third portion, movement of the restriction section in the first direction and in the second direction is restricted, the second portion is engageable with the fourth portion,
• the fourth portion has a contact surface that contacts the second portion in a state where the fourth portion is engaged with the second portion,
• the contact surface includes a flat surface parallel to the placement surface,
• when the placement surface is viewed from a direction orthogonal to the placement surface, two or more third portions of the plurality of third portions are included in a range in which the first portion is movable while maintaining a state in which the second portion contacts the flat surface,
• the fourth portion is provided at a position corresponding to a predetermined size of the medium, and
• the restriction section is configured to, when the first portion and the third portion are engaged in a state where the second portion and the fourth portion are engaged, enable to switch, via a user operation, the third portion that is engaged with the first portion while maintaining the state where the second portion and the fourth portion are engaged.