Cross is a pipe fitting with four branches in pairs, each pairs on one axis, and the axes at right angles. It has one inlet and three outlets, or vice versa. Crosses are common in fire sprinkler systems, but not in plumbing due to their extra cost as compared to using two tees.

Cross Arm Straps are durable anchorage connectors for many applications. The feature includes a pass-through loop end design for easy use. Cross arm straps are convenient end points for use with horizontal lifeline systems. These straps include a small and large D-ring pass through design for easy installation & use. Cross arm straps are convenient end points for a horizontal lifeline system. These are designed to wrap around structures to form a secure anchor point.

Cross-correlation flow measurement is a powerful technique for measuring flow based on the natural fluctuations. They are designed to use the properties of suspended solids to measure the flow. It is based on measuring the transition time of some types of disturbances, such as electrical resistance between two points in a flow system. Ultrasonics is commonly used with cross correlation flow meter. Random variations of conductivity, pressure and temperature are the basis of this type of flowmeter. Cross-correlation techniques are used for the linear measurement of speed with two retro-reflected infrared beams. This flowmeter is applied for the measurement of the velocity of hot steel strip in a high-speed rolling mill. They are available for the measurement of the mass flow of solids in pneumatic conveying systems.

Cross counter flow heat exchangers are also called as cross flow heat exchangers. In cross flow arrangement, the flow may be called mixed or unmixed, depending on the design. In this arrangement, hot and cold fluids flow through individual flow channels with no fluid mixing between adjacent flow channels. In this case, each fluid stream is said to be unmixed.