Locate the bonnet release handle: It is usually located on the driver's side footwell, near the dashboard.
Remove the bonnet release handle: There is a small cover that needs to be pried off, then you can unscrew the two bolts that hold the handle in place. You may need a screwdriver or other suitable tool to assist with this.
Insert a long, thin object: Once the handle is removed, you will see a small hole where the cable would normally go. Insert a long, thin object, such as a screwdriver or a piece of wire, into this hole.
Reach and pull the emergency bonnet release lever: The emergency bonnet release lever is located inside the bonnet, on the driver's side. You may need to use a flashlight to see it clearly. Once you have found the lever, pull it to release the bonnet.
Lift the bonnet: Once the lever is pulled, you should be able to lift the bonnet and access the engine compartment.
Please note that this procedure may vary slightly depending on the specific year and model of your Renault Master. If you have any concerns or are not comfortable performing this procedure yourself, it is recommended to consult a qualified mechanic or refer to your vehicle's owner's manual for specific instructions.