Hook device for stretching curtain on rack assembly

A hook device installed on a column having at least a first groove, a second groove, and a third groove for connecting and stretching a curtain, comprising:

• a base having a first wall and, extending respectively from two lateral edges of said first wall, a second wall and a third wall, and an extension piece extending outward along the edge between said first and second walls;
• said first, second, and third walls jointly forming a space threaded by said first, second, and third grooves of said column;
• said extension piece having at least a through hole;
• at least a first wheel, a second wheel, and a third wheel configured in said space to said first, second, and third walls, respectively;
• said first, second, and third wheels slidably embedded in said first, second, and third grooves of said column, respectively;
• and
• at least an elastic hook element connecting said curtain;
• said elastic hook element configured on said through hole of said extension piece;
• wherein said elastic hook element contains a first shaft, a second shaft, a tubular sleeve, a first spring, a nut, a second spring, and a hook piece;
• said first shaft has a first end threaded through said through hole of said extension piece, said tubular sleeve, and said first spring;
• said first end of said first shaft is then fastened by said nut;
• said first shaft has a second end pin-joined to a first end of said second shaft;
• and said second shaft has a second end threaded through said hook piece and said second spring.