To fit a rig to your ship, you must have the Jury Rigging skill trained to the required level, open rig slots, and sufficient calibration capacity to fit the rig. Jury Rigging requires Mechanic to be trained to level 3. A rig's information window will display the amount of calibration is required to fit the rig to your ship.
Low slots are a category of module slot found on ships in EVE. Generally, low slots contain passive modules which improve ship performance. Armor tanking modules occupy low slots. Some low slot modules share purposes with mid slot modules, but the details of their use differ. This page is a collection of all the types of modules that use low slots.

Rigs are permanent ship modifications that fit into the rigging slots of a ship. Once fit, in most ships they must be destroyed in order to be removed (unlike regular modules). The exceptions are T3 Strategic Cruisers which feature removable rigs. Most rigs have some other drawback associated with them; these penalties are reduced by training more levels in the associated rigging skill: the amount of speed reduction caused by armor rigs, for example, is lessened (though never completely eliminated) by your Armor Rigging skill. However, if you're willing to face the full downside, you can fit any rig with no skills whatsoever.

Rigs fit into rig slots, and, just like modules, each rig takes up one rig slot. Tech 1 ships have 3 rig slots, Tech 2 ships have 2, and a few ships (notably Freighters, Jump Freighters, Corvettes, and Shuttles) have none. Rigs come in four sizes: Small, for Frigates and Destroyers. Slot layout: 2 turrets, 2 high, 4 mid, 4 low, and 3 rigs; The Astero can be bought in most regional markets. Blueprints can be obtained by contract, or on the market, or by accumulating enough Servant Sister’s Of EVE loyalty points. In the hands of an alert pilot, the Manticore is one of the hardest ships to kill in New Eden. Each ship has a specific number of hardpoints, which are places to attach turret modules, launcher modules, rigs, and subsystems. Weapon hardpoints will limit the amount of a type of weaponry a ship can use. For example, the Caldari Raven battleship has a total of eight high slots. The ship's bonuses are aimed at missiles so you would normally want to fill all eight slots with missile.

Rigs don't have powergrid or CPU fitting requirements, but instead require calibration, a rig-specific fitting resource. All ships have 400 calibration points, except for pirate faction ships which have 350. A Tech 1 rig requires between 50 and 250 calibration points, with Tech 2 variants requiring 50% more calibration than their Tech 1 equivalents.

Rigs fit into rig slots, and, just like modules, each rig takes up one rig slot. Tech 1 ships have 3 rig slots, Tech 2 ships have 2, and a few ships (notably Freighters, Jump Freighters, Corvettes, and Shuttles) have none.

Rigs come in four sizes:

Small, for Frigates and Destroyers
Medium, for Cruisers, Battlecruisers, Industrials, and Mining Barges
Large, for Battleships
Capital, for Capital Ships

Unlike for modules, it's not possible to fit a 'wrong-sized' rig on a ship. Nearly all rigs come in all four sizes, with identical stats for each size.

Rigs are manufactured by players, using salvaged material.

Armor

See also: Armor Tanking and Guide to Logistics

The downsides of armor rigs can be mitigated by training Armor Rigging.

Name	Effect	Downside
EM Armor Reinforcer	Increase armor resistance to EM damage	Decreases ship's maximum velocity
Explosive Armor Reinforcer	Increase armor resistance to explosive damage
Kinetic Armor Reinforcer	Increase armor resistance to kinetic damage
Thermal Armor Reinforcer	Increase armor resistance to thermal damage
Auxillary Nano Pump	Increase amount a local armor repair module repairs per cycle	Increases armor repairer powergrid requirements
Nanobot Accelerator	Decrease local armor repair module cycle time^[1]	Increases armor repairer powergrid requirements
Remote Repair Augmentor	Reduces capacitor used by remote armor repair modules	Decreases ship's maximum velocity
Transverse Bulkhead	Increases hull hit points by a percentage	Decreases ship's cargo capacity
Trimark Armor Pump	Increases armor hit points by a percentage	Decreases ship's maximum velocity

^This is not subject to stacking penalties, despite what the rig's description says.

Astronautic

The downsides of astronautic rigs can be mitigated by training Astronautics Rigging.

Name	Effect	Downside
Auxiliary Thruster	Increase maximum velocity	Decreases armor hit points
Cargohold Optimization	Increases cargo capacity^[1]
Dynamic Fuel Valve	Decreases the capacitor used by afterburners and microwarpdrives
Engine Thermal Shielding	Increases cycle duration of afterburners and microwarpdrives
Higgs Anchor^[2]	Increase mass and agility while greatly reducing maximum velocity	Reduces warp velocity
Hyperspatial Velocity Optimizer	Increases maximum warp velocity	Increases signature radius
Low Friction Nozzle Joints	Increases agility	Decreases armor hit points
Polycarbon Engine Housing	Increases maximum velocity and agility	Decreases armor hit points
Warp Core Optimizer	Reduces the capacitor needs for warping	Increases signature radius

^This only affects the 'normal' cargo bay, it doesn't increase the capacity of any 'special' cargo bays (e.g. ore hold, fleet hangar, etc)
^Only one Higgs Anchor rig can be fit to a ship at time. Additionally, there is no Tech 2 variant of this rig.

Drone

See also: Drones

The downsides of drone rigs can be mitigated by training Drones Rigging.

Name	Effect	Downside
Drone Control Range Augmentor	Increases the drone control range	Decreases ship's CPU
Drone Durability Enhancer	Increases drones' hit points (armor, shield, and hull)
Drone Mining Augmentor	Increases the yield of mining drones and decreases cycle time for ice harvesting drones
Drone Repair Augmentor	Increases the amount repaired by repair drones
Drone Scope Chip	Increases the optimal range of drones' weapons
Drone Speed Augmentor	Increases the speed of drones
Sentry Damage Augmentor	Increases the damage of sentry drones
Stasis Drone Augmentor	Increases the amount by which stasis webifier drones reduce their target's velocity

Electronic superiority

See also: EWAR Guide

The downsides of electronic superiority rigs can be mitigated by training Electronic Superiority Rigging.

Name	Effect	Downside
Inverted Signal Field Generator	Increases the strength of remote sensor dampener modules	Decreases shield hit points
Particle Dispersion Augmentor	Increases the strength of ECM modules
Particle Dispersion Projector	Increases the range of EWAR modules^[1]
Signal Disruption Amplifier	Decreases the capacitor need for ECM (including Burst ECM) modules	No downside
Targeting Systems Stabilizer	Decreases the targeting delay after uncloaking	Decreases shield hit points
Tracking Diagnostic Subroutines	Increases the strength of t	Decreases shield hit points

Eve Rig Slots