The Strait-Line Laser Tape is a precision measuring device. The laser tape utilizes a visible laser beam -- aimed at a perpendicular wall surface. The device measures the length of time it takes to receive the reflected light of the beam back at the unit.
Install a 9-volt battery into the Strait-Line laser unit. Remove the battery compartment door and snap the battery connector onto the battery. Place the battery into the compartment and replace the cover.
Set the unit at the desired distance to be measured. If measuring something such as a piece of 2-by-4 lumber, lay the board on the floor and butt one end of the board against a hard vertical wall. Set the unit on the board and then press the "FT/M" button, to select the measurement denomination. FT will display the measurement in feet and inches: While M will provide the measurement in meters.
Aim the front of the laser tape toward the vertical wall, which will reflect the laser light back at the unit. Press the "Read" button on the button panel to take the measurement. If the measurement is to be taken while moving the unit, hold down the "Read" button, while moving the laser tape along the board. The unit will display the distance, as you change the position.
Press the button with an "L" above it, if you are taking an area measurement. After pressing this button, position the Strait-Line laser tape device at the furthest distance from the wall to be measured. When ready to take the first measurement -- which will be length -- press the "Read" button once.
Wait for the letter "W" on the readout to begin flashing: Then, take the measurement of the other wall, pressing the "Read" button one more time. After both measurements are made, the unit will calculate and display the total area.
The Strait-Line laser tape cannot measure through glass, even though the laser beam passes through glass. Glass interferes with the amount of reflected light being received by the unit.
Never stare into the laser beam. The laser beam coming from the Strait-Line laser tape is bright enough that permanent eye damage can result.