Drawbridge in the context of Major's Green

A fixed link or fixed crossing is a permanent, unbroken road or rail connection across water that uses some combination of bridges, tunnels, and causeways and does not involve intermittent connections such as drawbridges or ferries. A bridge–tunnel combination is commonly used for major fixed links.

This is a list of proposed and actual transport links between continents and to offshore islands. See also list of bridge–tunnels for another list of fixed links including links across rivers, bays and lakes.

The head of navigation is the farthest point above the mouth of a river that can be navigated by ships. Determining the head of navigation can be subjective on many streams, as the point may vary greatly with the size or the draft of the ship being contemplated for navigation and the seasonal water level. On others, it is quite objective, being caused by a waterfall, a low bridge that is not a drawbridge, or a dam without navigation locks. Several rivers in a region may have their heads of navigation along a line called the fall line.

Longer rivers such as the River Thames may have several heads of navigation depending on the size of the vessel. In the case of the Thames, that includes London Bridge, which historically served as the head of navigation for tall ships; Osney Bridge in Oxford, which has the lowest headroom of any bridge on the Thames that generally restricts navigation to smaller vessels such as narrowboats and cabin cruisers, and the long reach above St John's Lock, the first lock downstream of the river’s source, on the outskirts of Lechlade, where the river can become treacherously narrow and shallow for anything but small motorboats and human-powered vessels.

An advantage of making bridges moveable is the lower cost, due to the absence of high piers and long approaches. The principal disadvantage is that the traffic on the bridge must be halted when it is opened for passage of traffic on the waterway. For seldom-used railroad bridges over busy channels, the bridge may be left open and then closed for train passages. For small bridges, bridge movement may be enabled without the need for an engine. Some bridges are operated by the users, especially those with a boat, others by a bridgeman (or bridge tender); a few are remotely controlled using video-cameras and loudspeakers. Generally, the bridges are powered by electric motors, whether operating winches, gearing, or hydraulic pistons. While moveable bridges in their entirety may be quite long, the length of the moveable portion is restricted by engineering and cost considerations to a few hundred feet.

The corvus (Latin for "crow" or "raven") was a Roman ship-mounted boarding ramp or drawbridge for naval boarding, first introduced during the First Punic War in sea battles against Carthage. It could swivel from side to side and was equipped with a beak-like iron hook at the far end of the bridge, from which the name is figuratively derived, intended to anchor the enemy ship.

The corvus was still used during the last years of the Republic. Appian mentions it being used on August 11th 36 BCE, during the Battle of Mylae, by Octavian's navy led by Marcus Agrippa against the navy of Sextus Pompeius led by Papias.