Display member, head-up display device, and jig

A jig that holds a display member, the jig comprising:

• a first engaging member and a second engaging member that hold both sides of the member engaging unit, wherein
• the display member comprises:
• an optical surface on which a predetermined process is performed;
• and
• a member engaging unit that is linked to the optical surface and held by the first engaging member and the second engaging member, wherein,
• the member engaging unit includes:
• a thick portion, and
• a thin portion that is a size smaller than the thick portion and is linked to the thick portion,
• when the jig comes close and passes the thick portion, the first engaging member and the second engaging member are in a first relation where the first engaging member and the second engaging member are separated from each other,
• when the jig reaches the thin portion, the first engaging member and the second engaging member are in a second relation where the first engaging member and the second engaging member are closer to one another than in the first relation,
• at least in the second relation, both the first engaging member and the second engaging member are in a linear contact or a surface contact with the member engaging unit,
• the member engaging unit is held between the first engaging member and the second engaging member in the second relation, and
• the member engaging unit is held by the jig during the predetermined process.