Amazon.com: Bosch Professional FSN WAN angle guide for guide rail (compatible with all Bosch GKS Professional circular saws, GKS G-models, GKT plunge saws, selected GST jigsaws + GOF routers with adapter) :
Bora 530416 Quickcut Circular Saw Guide With Rail & Angle Assist, All-In-One Woodworking Tool, Strong Aluminum 16 Inches Long, With A 14-Inch (35.5Cm) Guide Rail - Amazon.com