How to open the upper left context menu via keystroke (for PuTTY on Windows)

Does anybody know a keystroke to open the upper left context menu in Windows operating systems? I'm referring to the one listling:

• Restore
• Move
• Size
• Minimize

• Maximize

• Close

In particular I want to restart individual 'inactive' putty sessions without using the mouse by any chance.

Solution 1:

You need to set System menu appears on ALT-Space or System menu appears on ALT alone in PuTTY's Windows | Behaviour settings.

Solution 2:

Just adding to the answer from Mike Fitzpatrick

In order for the changes to be effective, you need to:
Open the context menu (upper left) > Click Change Settings... > Windows (Left Pane) > Behaviour
Tick one of the items "System menu appears on.."
and click "Apply"