Like other line lasers, combination lasers have far less range than rotary models. The line from a rotary laser is a focused beam of light being spun in a 360-degree arc; a line laser's beam is more diffuse because it has passed through a lens that spreads it into a continuous line. It's like the beam on a flashlight – it becomes dimmer as it covers more area.
The range of these tools is listed in the spec tables. When used indoors, the range is highly dependent on the ambient lighting conditions: The brighter the surroundings, the harder it will be to see the line. Past a certain point, the line won't be visible to the naked eye – and then you'll have to use a target card, laser glasses, or a receiver to locate it. I find that I rarely need to use receivers indoors, because the lighting is dim and the distances are short enough to make out the beam. But outdoors, and especially over greater distances, the only way to detect the beam is with a receiver, which produces an audible beep or displays an icon on the screen to indicate that a beam is hitting it.
Receivers work only with models equipped with a pulse function. When the laser is set to pulse, the beam flicks on and off very rapidly – so rapidly it can only be detected by the receiver. In my experience, receivers are interchangeable within brands and usually between brands. This was the case with all but three of the tools we tested: The Agatec and Topcon LC-2 work with a receiver that doesn't work with other lasers, and the Bosch did not work with any of the receivers we had – though it does work with one from Bosch. If you need a receiver, it will be less expensive to buy it as part of the kit than to purchase it separately.Accuracy
Each model's accuracy is provided by the manufacturer, typically in the range of +/-3/8 inch at 100 feet. I double-checked some of the claims and found them to be fairly accurate. All the tools performed adequately in this category. We most often used these lasers over distances of less than 30 feet, and one could argue that in a typical application their accuracy is actually closer to +/-1/8 inch or even less. This should satisfy most residential and light commercial standards.
You can increase the accuracy of your work by always marking the same part of the line. It's up to you whether it's the top, bottom, left, right, or center. This is less of an issue with better lasers because their beams tend to remain tightly focused over greater distances.
When used indoors, the tools project visible continuous lines that can be used in place of marked layout on the floor (above left), up the walls, and across the ceiling (above). Lines are difficult to see outdoors and under bright lighting conditions, so it may be necessary to use a laser receiver (left) to detect beams too faint to be seen by human eyes.