Home / Double Swing Gates and the Drop Bolt
Double Swing Gates and the Drop Bolt
A double swing gate closes in the center, and the drop bolt, a steel rod that drops into a hole in the ground, is what holds the first leaf still so the second can latch against it. Using the bolt correctly, and keeping its sleeve clear of dirt, stops leaves from swinging in the wind and keeps the center joint aligned.
Why wide openings use two leaves
A single leaf across a wide opening would be long, heavy and difficult to support from one post. Splitting the opening into two leaves halves the length of each, which cuts the lever arm and lets each hinge carry less. Two leaves also let a narrow pedestrian opening be made by swinging only one.
The cost of the design is a center joint, where the leaves meet. That joint needs hardware that holds both leaves together when closed, and something to keep them from drifting when open.
The passive and active leaf
Most double gates have an active leaf, the one used for everyday passage, and a passive leaf that stays closed most of the time. The passive leaf is held shut by a bolt that drops into the ground. The active leaf latches against the passive one, so releasing the bolt frees both.
Which leaf is the active one depends on the traffic. A pedestrian-heavy property might choose the leaf nearer the walkway, and a delivery yard might use both equally. Marking which is which with a simple sign prevents confusion for visitors and new workers.
How a drop bolt works
A drop bolt is a vertical steel rod attached to the leaf, usually in a guide on the frame. At the bottom end, the rod slides into a sleeve set in concrete or pavement. Pulling the rod up releases the leaf, and letting it fall locks the leaf in place. Gravity does the work, which makes the mechanism simple and dependable.
The rod should be thick enough to resist bending when a gust pushes on the leaf. A rod that bends once will bind afterward. Heavy gates use rods of substantial diameter, sometimes with a second guide near the bottom to keep the rod straight.
The ground sleeve
The sleeve, also called a receiver, is a pipe or a socket set flush with the pavement. It must be deep enough to hold the rod firmly, and drained so water does not collect. A sleeve that fills with soil, gravel or water holds the rod poorly and may rust shut.
In Georgetown, where clay can swell and shrink, a sleeve set in a thin slab may shift. Setting it in a footing that moves with the post helps maintain alignment. A small cap or a hinged flap keeps debris out when the bolt is raised.
Cane bolts
A cane bolt is a related device, shaped like a walking cane. The bottom rod is bent at the top into a handle, so a user can lift and turn it to hold the rod in the raised position. It works well for lighter leaves and gates used by hand. The handle makes it easy to grip, and the rotation locks the rod up out of the hole when the gate must stand open.
For heavy commercial leaves, a heavier version with a welded guide and a thick rod is preferable, since a thin cane bolt can bend when a vehicle bumps the leaf.
The center latch
With the passive leaf secured, the active leaf needs its own latch at the center. Common choices include a gravity latch that drops into a keeper, a slam latch that engages automatically and a padlock hasp for locked service. The latch should lock to the passive leaf, not to a thin cover strip that could bend.
The gap between leaves should be small and even. A wide or slanted gap shows that a leaf has dropped or a post has moved, and it makes the latch less reliable. A small adjustable keeper allows fine tuning.
Holding a leaf open
Open leaves should be held. A drop rod set into a second sleeve at the open position, or a stop post with a latch, prevents the leaf from blowing back. A leaf left swinging can strike a vehicle, hurt a person or bend its own hinges. Wind in the area can be strong in spring, so the hold-open matters as much as the closing hardware.
Some gates use a spring-loaded catch that engages when the leaf reaches its full open position. That is convenient and reduces the chance of forgetting.
Automatic double gates
Where operators drive both leaves, the controller must sequence them so one opens slightly before the other, and closes in the reverse order, so the overlap does not jam. Drop bolts on automated gates are either removed or replaced with an electric lock that releases on command. An operator that tries to push a leaf with a bolt still down will damage itself or the leaf.
Common problems
- A bolt that no longer reaches the sleeve because the leaf sagged
- A sleeve packed with dirt or ice
- A bent rod that sticks halfway
- Misaligned leaves leaving a wide center gap
- A missing hold-open that lets a leaf slam
Most of these come down to alignment. Checking that both leaves are plumb, that hinge posts have not moved and that the sleeve sits directly beneath the rod catches problems early. A little time spent each season keeping the bolt, sleeve and latch clean and square keeps a double gate working smoothly for a long time.
Sizing the center overlap and stops
Where the two leaves meet, a slight overlap or a rabbeted edge helps hide the gap and gives the latch more steel to grab. A center stop, a short welded tab or a rubber bumper on one leaf, prevents the active leaf from swinging past its closed position and straining the latch. Without a stop, repeated hard closing gradually bends the latch bar and twists the frame.
Leaf height at the center should match across the joint. If one leaf has sagged lower than the other, the top rails no longer align and the latch binds. A quick check with a straightedge across the top of both rails shows whether the pair is level.
Winter and storm considerations
Water in a ground sleeve can freeze during one of the hard freezes that occasionally reach central Texas, and the expanding ice can lock the rod in place or crack a shallow sleeve. A small drain hole at the bottom of the sleeve, set into gravel, lets water escape. After heavy rain, a glance into the sleeve confirms it is clear before the next windy day, when the bolt must be able to drop fully.