# Charcoal, 17 bytes

    (Ｍ↙↓⁻θ¹Ｍ↑(Ｍ→↗Ｉθ‖Ｍ

[Try it online!](https://tio.run/##S85ILErOT8z5/1/j/Z61j9pmPmqb/Khx97kdh3aC@RMhwpMetU1/v2fluR2PGqYBBf7/NwYA)

**Explanation:**

    (                  // Print '('.
    Ｍ↙                // Move one step to the down and to the left.
    ↓⁻θ¹               // Draw a line of n-1 '|'s downwards.
    Ｍ↑(               // Move one step up and print '('.
    Ｍ→↗Ｉθ              // Move one step to the right and print a line of n '/'s.
                       // Now the left half of the shield is done.
    ‖Ｍ                // Mirror and copy the left half to finish the shield.