This is a simple window holder / wedge, which I created to be used against heavy drafts.

If it annoys you that in the summertime the drafts bang your windows all the time, then this model might be for you. It is specifically designed to be used with windows which can be partially open by tilting, as illustrated here:
 

To use just simply insert between the window frame and window as illustrated. The cutouts help with grabbing and removing this simple tool. The big contact area helps to disperse pressure on the lining.
For windows which are harder to reach from the side, I made a model with a simple elongated handle (this is included in the print profile):



I advice to use a pad on the side which will be in contact with the window frame to eliminate the risk of scratching. I used a pad with dimensions 20x20. This you can buy in any hardware store, usually they are used to protect the floor from scratches caused by furniture.



The current model calculates with a tilt angle of 6.3 degrees, in case this doesnt work for you, Im happpy to create a personalised one for your needs.