The Shield Grenade Launcher is an interesting support weapon. It fires a sticky grenade that projects a spherical shield after about a second after it latches onto something. The shield has a radius of about one meter and lasts for twice the amount of time you charge it by holding down the trigger. The maximum time the shield can last for is 15 seconds.
The primary fire will let things go out of the shield, but not in. The alt-fire does the reverse.
There are many tactical uses for the SiGL. For example, it can be used to render an enemy helpless via the alt-fire, or it can serve as a shield for an ally. You can also use this to temporarily block a path as well.
Please note that SiGL grenades will bounce off of existing shields.
Express your own tactics in the comments.