You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND 
       [0001]    A fire sprinkler system comprises a fire suppression agent supply system, one or more fire sprinklers, and a piping system connected between the supply system and the fire sprinklers. The fire sprinkler system can be installed in a variety of environments, such as factories, commercial buildings, homes, etc. One type of fire sprinkler system is a wet pipe system that comprises a water supply system, water piping, and one or more fire sprinklers. 
         [0002]    In order to install a fire sprinkler system, the piping system needs to be connected to the supply system and to the fire sprinklers. Typically, the pipes are installed close to the ceiling with a roughed-in outlet. A roughed-in outlet is part of plumbing work for the fire sprinkler system that is ready for future connection to a fixture (such as a sprinkler). The sprinklerfitter will then measure the drop from the roughed-in outlet of the pipe to where the sprinkler will connect. For example, in a nine-foot ceiling, the pipes may be installed close to the top of the ceiling. At each point in the piping below which a sprinkler is to be installed, the piping includes a roughed-in outlet. In an installation where the sprinklers are supposed to be installed at the drop-ceiling, the sprinklerfitter measures from the roughed-in outlet to the drop ceiling. In particular, the sprinklerfitter must move the ladder under each roughed-in outlet, climb the ladder, and take the measurement from the roughed-in outlet to the drop ceiling. Doing each of these steps for an installation with dozens (or possible hundreds) of sprinkler heads takes a considerable time. 
       SUMMARY 
       [0003]    The present embodiments relate to a sprinkler drop ruler. In one aspect, the sprinkler drop ruler is provided. The sprinkler drop ruler may comprise: a rigid frame having an opening; a handle connected to the rigid frame and in fixed relation to the rigid frame; and a ruler with an end shaped to seat in the opening and configured to move inside or along a side of the handle in order to measure a sprinkler drop. The ruler may be positioned at least partly within the handle so that the ruler is configured to move within the handle. Further, the handle may be connected to the rigid frame so that the opening of the rigid frame is co-axial with the handle. Moreover, the end of the ruler can be rectangular in shape and the opening of the rigid frame is also rectangular in shape and matched to seat the end of the ruler. The sprinkler drop ruler may further include a window connected to the handle with the window being at least partly transparent and include indicia so that the ruler is visible through the window. 
         [0004]    In another aspect, a method for measuring a sprinkler drop is provided. The method includes using a sprinkler drop ruler that includes: a rigid frame having an opening; a handle connected to the rigid frame and in fixed relation to the rigid frame; and a ruler with an end shaped to seat in the opening and configured to move inside or along a side of the handle in order to measure a sprinkler drop. The method further includes the sprinklerfitter holding the handle in one hand, and the sprinklerfitter moving the ruler with another hand until the end of the ruler comes in contact with the roughed-in outlet. When the end of the ruler is contacting the roughed-in outlet, the sprinklerfitter may read the measurement of the ruler. 
         [0005]    Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of the sprinkler drop ruler. 
           [0007]      FIG. 2  is a top view of the rigid frame of the sprinkler drop ruler. 
           [0008]      FIG. 3  is a top view of the top of the ruler of the sprinkler drop ruler. 
           [0009]      FIG. 4  is a perspective view of the handle and the ruler of the sprinkler drop ruler. 
           [0010]      FIG. 5  is a front view of one example of the window, extension piece, and rails. 
           [0011]      FIG. 6  is a perspective view of another example of the extension piece. 
           [0012]      FIG. 7  is a perspective view of the sprinkler drop ruler in operation. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    A sprinkler drop ruler  100  embodying one example of the present invention is illustrated in  FIG. 1 . The sprinkler drop ruler  100  includes a rigid frame  102 , a handle  108 , and a ruler  116 . The rigid frame  102  may be any type of rigid structure, such as metallic (e.g., aluminum), plastic (e.g., plexiglass), or the like. Further, the rigid frame  102  may be transparent (in order to see through the rigid frame  102 ), translucent or opaque. The rigid frame  102  is shown in  FIG. 1  as rectangular in shape. The rigid frame  102  may be composed of other shapes, such as square or round. The rigid frame  102  further includes an opening  104  through which the ruler  116  may slide. The opening  104  is illustrated as rectangular in shape. As discussed in more detail below, the opening  104  may be other shapes, such as square or round. 
         [0014]    As discussed in the background, the sprinkler is positioned at the approximate height of the ceiling tile lattice structure (the structure that holds the ceiling tiles in place). The length of the sprinkler drop from the roughed-in outlet to the sprinkler is measured from the roughed-in outlet to the ceiling tile lattice structure. In order to obtain this measurement with the sprinkler drop ruler  100 , the rigid frame  102  may be pushed against the ceiling tile lattice, and the ruler  116  is slid upward until it contacts the roughed-in outlet in order to measure the sprinkler drop. Thus, in one embodiment, the size of the rigid frame  102  is equal to or larger than an opening in the ceiling tile lattice. This is depicted in  FIG. 7 , discussed below. For example, the ceiling tile lattice may comprise 2′×2′. So that, in one embodiment, the rigid frame  102  in one dimension is equal to or greater than 2′ (and in another dimension can be 2′ or less, such as 1′ or less). As another example, the ceiling tile lattice may comprise 1′×1′. So that, in one embodiment, the rigid frame  102  in one dimension is equal to or greater than 1′. In this way, when the operator presses the rigid frame  102  against the ceiling tile lattice, the rigid frame  102  is stopped by the ceiling tile lattice. 
         [0015]    The sprinkler drop ruler  100  further includes the handle  108 . A perspective view of the handle  108  is illustrated in  FIG. 4 . The handle  108  can be a variety of lengths, such as 4′-0″ for an 8′ ceiling and 5′-6″ for a 10′ ceiling. These lengths are merely for illustration purposes. The handle  108  is connected to rigid frame  102 . As shown in  FIG. 1 , the handle  108  is in fixed relation to the rigid frame  102  so that the opening  104  of the rigid frame  102  is coaxial with the handle  108 . In one embodiment, the cross-section of the handle  108  is identical to the opening  104 , as shown in  FIG. 1 . In an alternate embodiment, the cross-section of the handle  108  may be different from the opening  104 , such as bigger than the opening  104 . 
         [0016]    The shape of the handle  108  may be such that the ruler  116  slides adjacent to or within the handle  108 . As illustrated in  FIG. 4 , the handle  108  is illustrated as having a C cross-section, with element  109  indicating the “C” shape; though other shapes may be used which enable the ruler  116  to slide therein. Alternatively, the ruler  116  may slide inside the handle  108 . For example, the ruler  116  may slide along a side of the handle  108 . Moreover, one end of the ruler  116  may extend beyond an end of the handle  108  even when the top  106  of the ruler is seated in rigid frame  102 . For example, ruler  116  can extend 1′, 2′, 3′, or more from the end of the handle, as shown in  FIG. 1 . 
         [0017]    The sprinkler drop ruler  100  may further include extension piece  110 . The extension piece  110  may be connected to handle  108 , or the extension piece  110  may be integral with handle  108 . As discussed in more detail with respect to  FIG. 6 , the extension piece  110  may be used to calibrate the sprinkler drop ruler  100 . Extension piece  110  may further include a window  112 . The window  112  may be transparent so that the ruler  116  may be seen therethrough. The window  112  may include one or more indicia  114  to indicate how far the top  106  of the ruler  116  is above the rigid frame  102 . For example, when the top  106  of the ruler  116  is flush with the rigid frame  102 , the indicia  114  points to “0” of the ruler, indicating that the distance from the top  106  of the ruler  116  to the rigid frame  102  is zero inches. Calibration of the sprinkler drop ruler  100  is discussed below with respect to  FIGS. 5-6 . 
         [0018]      FIG. 2  is a top view of the rigid frame  102  of the sprinkler drop ruler  100 . The dimensions of the rigid frame  102  may be 2′ 6″×4″, as shown in  FIG. 2 . These dimensions are merely for illustration purposes. Other dimensions are contemplated. As discussed above, the rigid frame  104  includes an opening  104  through which the ruler  116  may slide. The opening  104  may further include a seat or a lip  118  upon which an underside of the top  106  of the ruler  116  may be seated.  FIG. 3  is a top view of the top  106  of the ruler  116  of the sprinkler drop ruler  100 . The top  106  may be composed of a rubberized or other elastic material and may be shaped such that the top  106  fits into opening  104  and abuts seat  118 . Further, the top  106  may be a 2″×2″ square or may be rectangular in shape. 
         [0019]      FIG. 7  illustrates the sprinkler drop ruler  100  in operation. When the ruler  116  is in the fully retracted position (with the top  106  of the ruler  116  flush against the seat  118 ), the top  106  of the ruler is flush with the top of the rigid frame. This is considered the “0” position of the ruler for calibration purposes (e.g., the indicia  114  point to “0” on the ruler  116 ). Further, the sprinklerfitter may hold the handle  108  in one hand up against the ceiling tile lattice. Typically, the ceiling tile lattice is installed, but the ceiling tiles have not yet been installed. In this way, the sprinklerfitter can see the roughed-in pipe outlet. With the other hand, the sprinklerfitter can move the ruler  116  upward until the top  106  of the ruler reaches the roughed-in pipe outlet. When the top  106  of the ruler  116  contacts the roughed-in pipe outlet, the sprinklerfitter can then read the measurement in the window  112 , thereby recording the distance of the sprinkler drop. In this way, the measurement is a face-to-face measurement from the ceiling grid to the roughed-in pipe outlet. 
         [0020]    As discussed above, the sprinkler drop ruler may  100  be calibrated. The calibration may be done at manufacture or may be done after purchase. Calibration may comprise “zeroing” out the ruler so that when the top  106  of the ruler  116  is flush with the rigid frame  102 , the indicia  114  in the window  112  indicates “0” for the ruler. There are a variety of ways in which to calibrate the sprinkler drop ruler  100 . One way is to keep the extension piece  110  stationary and move the window  112  and the indicia  114 . The window  112  and the indicia  114  are in fixed relation to one another. The sprinkler drop ruler  100  may be calibrated by moving the window  112  so that the indicia  114  (fixed relative to the window  112 ) moves as well. When the top  106  is flush with the rigid frame  102 , the window  112  is moved until the indicia  114  point to “0” in the ruler.  FIG. 5  illustrates one example of adjusting the window  112  in which the window  112  may be moved either up or down based on one or more guides or rails  120 . In practice, the window  112  may be moved so that the indicia  114  points to “0” when the top  106  is flush with the rigid frame  102 . 
         [0021]    Another way is to move the extension piece  110  along with the window  112  and the indicia  114 . The extension piece  110 , the window  112  and the indicia  114  are in fixed relation to one another. The sprinkler drop ruler  100  may be calibrated by moving the extension piece  110  so that the window  112  and the indicia  114  (which are both fixed relative to the extension piece  110 ) moves as well. In practice, when the top  106  of the ruler  116  is flush with the rigid frame  102 , the extension piece  110  may be moved upward or downward (with the window  112  and the indicia  114  moving along with the extension piece  110 ) so that the indicia  114  points to “0”. 
         [0022]    Still another way to calibrate the sprinkler drop ruler  100  is to move the indicia  114 . The indicia  114  may be movable upward or downward independent of the window  112 . In practice, when the top  106  of the ruler  116  is flush with the rigid frame  102 , the indicia  114  may be moved so that the indicia  114  points to “0”. 
         [0023]    While the invention has been described with reference to various embodiments, it should be understood that many changes and modifications can be made without departing from the scope of the invention. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.

Summary:
A sprinkler drop ruler is provided for measuring the sprinkler drop from a roughed-in outlet. The sprinkler drop ruler includes a rigid frame having an opening, a handle connected to the rigid frame and in fixed relation to the rigid frame, and a ruler with an end shaped to seat in the opening and configured to move inside or along a side of the handle in order to measure a sprinkler drop. The sprinklerfitter may thus use the sprinkler drop ruler in order to measure the sprinkler drop. In this way, the sprinklerfitter does not need to climb a ladder to measure the sprinkler drop.