1. Introduction
This manual provides essential information for the safe and effective use of your Stack-On GCB-18C Steel 18-Gun Convertible Security Cabinet. Please read all instructions carefully before assembly and operation. Retain this manual for future reference.
The Stack-On GCB-18C Steel 18-Gun Convertible Security Cabinet is designed for secure storage of firearms. This cabinet meets California Department of Justice standards for safely storing firearms.

Figure 1: Stack-On GCB-18C Steel 18-Gun Convertible Security Cabinet.
2. Safety Information
WARNING: This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, visit P65Warnings.ca.gov.
- Always store firearms unloaded and locked.
- Keep keys secured and out of reach of children and unauthorized individuals.
- This cabinet is designed for security against unauthorized access, not for fire or water protection.
- Ensure the cabinet is securely mounted to a floor or wall to prevent tipping.
3. Package Contents
Verify that all components are present before beginning assembly:
- Stack-On GCB-18C Security Cabinet
- Adjustable Barrel Rests
- Metal Shelf (1)
- Keys (2)
- Mounting Hardware (bolts, nuts)
- Instruction Manual
4. Setup and Assembly
4.1 Choosing a Location
Select a discreet, dry, and secure location for your cabinet. Ensure the floor or wall can support the weight of the cabinet and its contents.

Figure 2: Cabinet shown next to a person for approximate scale.
4.2 Mounting the Cabinet
The cabinet features pre-drilled mounting holes for secure attachment to a floor or wall. Use the provided fastening hardware. For optimal security, it is recommended to anchor the cabinet to both the floor and a wall stud.

Figure 3: Cabinet dimensions (18"D x 21"W x 55"H) for planning installation.
4.3 Installing Shelves and Barrel Rests
The cabinet includes one metal shelf and adjustable barrel rests. The barrel rests are designed to accommodate various firearm sizes, including scoped rifles. The cabinet can be converted to shelving for storing ammunition, pistols, or other items by adjusting the internal configuration.

Figure 4: Interior view showing adjustable shelving and barrel rests for firearm and accessory storage.
5. Operating Instructions
5.1 Locking and Unlocking
The cabinet is equipped with a 3-point locking system and a key-coded cylinder lock. Insert the key and turn to engage or disengage the locking mechanism. Ensure the door is fully closed before locking.
5.2 Storing Firearms and Accessories
Place firearms in the designated barrel rests. Utilize the adjustable shelf for ammunition, pistols, or other valuables. Avoid overcrowding the cabinet to prevent damage to contents or the cabinet itself.
6. Maintenance
- Regularly inspect the locking mechanism for smooth operation.
- Keep the interior and exterior of the cabinet clean and dry.
- Periodically check mounting bolts to ensure they remain tight.
- Do not use harsh chemicals or abrasive cleaners on the cabinet's finish.
7. Troubleshooting
7.1 Door Not Closing Properly
- Check for obstructions inside the cabinet.
- Ensure the cabinet is level and securely mounted.
7.2 Key Difficult to Turn
- Apply a small amount of graphite lubricant to the key and insert into the lock.
- Do not force the key.
8. Specifications
| Feature | Detail |
|---|---|
| Model | GCB-18C |
| Dimensions (D x W x H) | 18" x 21" x 55" |
| Material | Steel |
| Color | Black |
| Lock Type | Double-Bitted Key Lock (3-point system) |
| Weight | 75 lbs |
| Capacity | Up to 18 firearms (actual capacity varies with accessories) |
| Mounting Type | Floor Mount |
| Included Components | Shelves, Barrel Rests, Mounting Hardware, Keys |
9. Warranty and Support
For warranty information or technical support, please contact Stack-On customer service. Refer to the product packaging or the official Stack-On website for current contact details.
Online resources may be available at the Stack-On Store on Amazon.





