sight glass
sight hole

But check the sight glass daily to make sure that the problem doesn't happen again.

Check the sight glass weekly and add water whenever the level drops.

Sight glasses were attached to the left-hand side of the engine.

The sight glass is usually mounted on the outside of the burner-boiler cabinet.

With high dome design, volume sight glass and lighted power switch.

Fuel quantity is indicated by sight glasses in the wing roots.

It's made of 7 gauge steel construction with a copper discharge line and oil level sight glass.

(With some older systems the cabinet may have to be opened to read the sight glass.)

Henry lifted the Kawasaki onto its center stand and bent over to check the oil level through the sight glass.

Its most distinctive identifying feature is the cooling water level sight glass on the right side of the long hood.

Engine water level sight glass on the rear upper right-hand side of the long hood.

Other inventions were the sight glass, and the udometer.

Today, however, sophisticated float switches have replaced sight glasses in many such applications.

The ceramic water tank atop the refrigerator was only a quarter full when she checked the sight glass.

The operation of the system is monitored via sight glasses and electronic measuring instruments.

Before draining any water, first check the sight glass to make sure that there is water in the boiler.

The old man moved a parchment and picked up a peculiar-looking device with a sighting glass in one end of it.

Most have a sight glass, usually a vertical glass tube, mounted on them for checking the fuel level.

The strongest sight glasses are made with borosilicate glass, because of the greater difference in its coefficient of expansion.

If, however, the sight glass reads low and the furnace does not shut off automatically, then a service technician should check out the cutoff valve.

A sight glass on the backwash vent line gives visible indication of the progress of washing.

The separator may therefore be combined with some other liquid level sensing mechanism such as a sight glass or float sensor.

Sight glasses enable operators to visually observe processes inside tanks, pipes, reactors and vessels.

During operation, the boiler's water level is constantly monitored, normally via a transparent tube referred to as a sight glass, or with a gauge.

Early versions sported the traditional overflow plug, which was replaced by the sight glass in 1978 to conform to German import requirements.

Some still have sighting holes so residents can shoot at anyone at his front door!

The relascope has a sight hole on the back and a clear window at the front to allow the user to sight through the tool.

The former featured a flexible rear tang sight mounted behind the hammer and the latter had the sight hole plugged.

The outer shells are equipped with nozzles for pipe and instrument connections, access doors, air blast doors, gas outlets, and sight holes.

The device is used by moving the sights until the observer can peek through the nearer sighting hole and view the cross hairs in the further sight aligned with the fire.

It was a 4-foot rod with a scale, a sighting hole at one end, and a wedge that could be moved along the rod to exactly obscure the disk of Sun or Moon.

Push the bend on to the outlet and, holding the other bend against the downpipe, mark the length of the pipe required using the 'sight holes' in the bends and cut it off.

After several lines, Swift-Killer would take another look through the sighting holes to make sure that the beam was being sent off in the right direction, while the flare crew replaced their flares with fresh ones.

Variations include reducing coupling nuts, for joining two different size threads; sight hole coupling nuts, which have a sight hole for observing the amount of engagement; and coupling nuts with left-handed threads.