Security Hinges With Studs: Single-Pin or Twin-Pin, and Which Size

Updated 2026-11-08 · RAYEN 雷茵

What does the stud do?

On an outward-opening door, the hinge knuckles face outside. Somebody who knocks out the pins could, on a plain hinge, lift the door off the frame. The stud is there for that case. With the door closed, it bridges the two leaves, so the door edge stays engaged with the frame even without the pin.

That is the design intent. It is a feature you can see on the drawing, not a rating, so judge it on the door it goes into.

Single-pin or twin-pin: what is the difference?

You can see it on the drawings.

• Twin-pin: each leaf carries one stud and one hole, at different heights. When the leaves fold together, each stud meets the hole opposite. That gives two studs per hinge, one in each direction.
• Single-pin: one leaf carries a stud and the other leaf carries the matching hole, at the same height. That gives one stud per hinge.

Both kinds keep the ordinary screw holes as well. The stud and its hole sit among them.

Which security hinges are there?

• 4x4x3.0-4BB Double Security Stud: twin-pin, 101.6 × 101.6mm, 3mm, Ø14.2mm, stainless 304/201.
• 5x4x3.0-4BB Double Security Stud: twin-pin, 127 × 101.6mm, 3mm, Ø14.2mm, stainless 304/201.
• 6x4x3.5-4BB Single Security Stud: single-pin, 152.4 × 101.6mm, 3.5mm, Ø16.2mm, stainless 304/201.
• 8x4x3.5-4BB Single Security Stud: single-pin, 203.2 × 101.6mm, 3.5mm, Ø16mm, brass.

All four have four ball bearings. The stainless ones come in Satin Sanded and the brass one in Frosted Copper.

Each security hinge has a plain twin on the same leaf. 4x4x3.0-4BB, 5x4x3.0-4BB and 6x4x3.5-4BB read the same in leaf, thickness and knuckle. So you can use a plain hinge in the middle and security hinges at top and bottom without changing the recess, as long as the hole positions suit your door.

How do the sizes compare?

Sorted by leaf thickness: the twin-pin hinges are 3mm and the single-pin hinges 3.5mm. The 4mm leaves at the end are brass hinges without studs.

What should you check on the door?

• Which way it opens. The stud matters most where the knuckles are on the outside.
• Leaf size the door and frame can take.
• Door weight and height, so we can check the hinge and how many to fit. No load figure is printed for these hinges.
• Whether the frame can take the stud hole. The stud must enter the opposite leaf, so nothing behind that leaf may block it. Check the drawing against your frame section.

A worked example

An apartment entrance door opens outwards. It is 2100mm high, timber, and the frame is cut for a 4 × 4in hinge. Use 4x4x3.0-4BB Double Security Stud at the hinge positions you want protected. If the middle hinge is plain, choose 4x4x3.0-4BB, which shares the 101.6 × 101.6mm leaf. Send us the door weight and the frame section, and we confirm the count and the stud clearance.

For a tall, heavy door where you want a long leaf, 8x4x3.5-4BB Single Security Stud is 203.2mm high in brass. Its stainless counterpart in that size is 8x4x3.5-6BB, which has six bearings but no stud.

Does the finish match the plain hinges?

Yes, in stainless. The twin-pin and single-pin stainless hinges are Satin Sanded, the same as their plain twins, so a mixed door shows one finish. The brass 8x4x3.5-4BB Single Security Stud is Frosted Copper. Keep brass and stainless off the same door unless the design asks for it.

What should you write on the order?

• Full code with the words twin-pin security or single-pin security.
• Leaf size, thickness and knuckle in mm.
• Material: stainless with grade, or brass.
• Finish and quantity.
• How many plain hinges, if you mix them on one door.

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