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You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional patent application Ser. No. 61/020,890, filed by the same inventor on Jan. 14, 2008, now pending. 
     
    
     BACKGROUND 
       [0002]    Scaffold frames are widely used in the construction trades to provide workers with easy access to the entire surface areas of walls. Horizontal rungs on a scaffold frame support walkboards that bear the weight of a worker with tools and materials. The most commonly used open scaffold frame has three vertical supports on each end, with rungs at only two height positions at an “open” side and rungs at four height positions on a “closed” side. Workers typically use the rungs on the “closed” side to support walkboards because the top rung on the open side is too high and the bottom rung too low for safe, productive use. These limitations on walkboard position may require that the scaffold be repeatedly torn down and restaged, reducing productivity and increasing possibilities for mishaps. 
       SUMMARY  
       [0003]    Additional support rungs may be added to the “open” sides of construction scaffolds by installing walkboard supports that hook onto upper scaffold rungs on an open side and are prevented from swinging by saddles that engage lower scaffold rungs. Ladder rungs within the walkboard support may be used for ascending a scaffold. Pairs of walkboard supports attached to opposing open sides may be used to add walkboards that span the ladder rungs within the open sides, allowing users to add more space to a work area in convenient position, reducing the amount of reaching and lifting a worker must do and the number of trips to the ground for additional tools and materials. All of these features and advantages of the present invention, and more, are illustrated below in the drawings and detailed description that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  shows a perspective view of a ladder and walkboard support being installed in a construction scaffold. 
           [0005]      FIG. 2  shows a perspective view of a ladder and walkboard support installed in a construction scaffold supporting additional walkboards. 
           [0006]      FIG. 3  shows a front elevational view of a ladder and walkboard support. 
           [0007]      FIG. 4  shows a side elevational view of a ladder and walkboard support. 
           [0008]      FIG. 5  shows a perspective view of a security pin being installed in a hook. 
           [0009]      FIG. 6  shows a perspective view of a security pin installed in a hook. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In the Summary above and in the Detailed Description, and the claims below, and in the accompanying drawings, reference is made to particular features (including method steps) of the invention. It is to be understood that the disclosure of the invention in this specification includes all possible combinations of such particular features. For example, where a particular feature is disclosed in the context of a particular aspect or embodiment of the invention, or a particular claim, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects and embodiments of the invention, and in the invention generally. 
         [0011]    The term “comprises” and grammatical equivalents thereof are used herein to mean that other components, ingredients, steps, etc. are optionally present. For example, an article “comprising” (or “which comprises”) components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. 
         [0012]    Where reference is made herein to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously (except where the context excludes that possibility), and the method can include one or more other steps that are carried out before any of the defined steps, between two of the defined steps, or after all the defined steps (except where the context excludes that possibility). 
         [0013]    The term “at least” followed by a number is used herein to denote the start of a range beginning with that number (which may be a range having an upper limit or no upper limit, depending on the variable being defined). For example, “at least 1” means 1 or more than 1. The term “at most” followed by a number is used herein to denote the end of a range ending with that number (which may be a range having 1 or 0 as its lower limit, or a range having no lower limit, depending upon the variable being defined). For example, “at most 4” means 4 or less than 4, and “at most 40%” means 40% or less than 40%. When, in this specification, a range is given as “(a first number) to (a second number)” or “(a first number) (a second number),” this means a range whose lower limit is the first number and whose upper limit is the second number. For example, 25 to 100 mm means a range whose lower limit is 25 mm, and whose upper limit is 100 mm. 
         [0014]    A ladder and walkboard support that comprises an embodiment of the present invention provides users with a simple and safe way to add rungs to the “open” side of a scaffold frame. As shown in  FIG. 1 , a typical scaffold frame  100  as is known in the art is generally rectangular with at least a first vertical post  102 , a second vertical post  104 , and a third vertical post  106  comprising each end of the frame. The vertical posts on each end are joined by at least an upper horizontal scaffold rung  108  and a lower horizontal scaffold rung  109 . The second and third posts  104 ,  106  are joined by two scaffold rungs, creating an open side  110  of the scaffold through which a person can easily step to reach the interior of the scaffold. The first and second posts  102 ,  104  are joined by more than two scaffold rungs, creating a closed side  112  of the scaffold that can support one or more walkboards  114  at several levels. The ends of the scaffold frame mirror one another and are joined by struts  116 . 
         [0015]    At least one walkboard  114  spans the ends of the scaffold, resting at each end of the walkboard on a scaffold rung at the same level, creating a long, level platform on which a worker can stand and rest tools and materials. In practice, workers often prefer to have several walkboards on which to rest tools and materials at levels that minimize the need for bending and reaching. Disadvantageously, the widely-spaced scaffold rungs  108 ,  109  on the open side  110  of the scaffold limit their choices to too high and too low. 
         [0016]    More convenient intermediate rungs can be quickly and safely added with a ladder and walkboard support  150  that attaches easily to the scaffold  100 . As shown in  FIG. 3 , an embodiment of such a ladder and walkboard support  150  comprises two vertical members  300  joined by at least two horizontal ladder rungs  302 . A hook  304  at the top of each vertical member and a saddle  306  at the bottom of each vertical member are sized and shaped to engage scaffold rungs. 
         [0017]    As shown in  FIG. 4 , each hook  304  is preferably formed and attached to a vertical member  300  so that the hook  304  is centered with respect to the central axis of the vertical member  300 . Each hook  304  has a lower throat portion  308  that is horizontally open on one side to allow a user to move the hook  304  horizontally against a scaffold rung, then drop the ladder and walkboard support  150  straight down to engage the scaffold rung. Centering the hook with respect to the central axis of the vertical member minimizes the tendency of the ladder and walkboard support to swing when suspended from a scaffold rung and weighted by a walkboard. 
         [0018]    Each saddle  306  is also preferably centered with respect to the central axis of a vertical member  300 . Each saddle has two arms extending downward to engage a scaffold rung and prevent the lower end of the ladder and walkboard support from swinging when mounted on a scaffold. A first saddle arm  310  preferably extends downward further than a second saddle arm  312  and is preferably oriented to the side of the ladder and walkboard support  150  to which the throat  308  of the corresponding hook  306  opens. 
         [0019]    The ladder and walkboard support  150  may be constructed from a variety of known materials but is preferably made from steel or other materials similar to those used in a scaffold, using well-known manufacturing methods. 
         [0020]    Returning to  FIG. 1 , a user attaches a ladder and walkboard support  150  to a scaffold  100  by resting the inner surfaces of the tips of the first saddle arms  310  against a lower scaffold rung  109  in an open side  110 , pivoting the ladder and walkboard support  150  about the lower scaffold rung  109  while swinging the hooks  306  toward the upper scaffold rung  108  until the upper scaffold rung  108  passes through the throat  308  of each hook  306 , then dropping the ladder and walkboard support  150  downward until the hooks  306  hang from the upper scaffold rung  108  and the lower scaffold rung  109  rests between the first and second saddle arms  310 ,  312  in the manner shown in  FIG. 2 . The lengths of the vertical members  300  are chosen so that the hooks  304  and saddles  306  will fully engage upper and lower scaffold rungs  108 ,  109  when the ladder and walkboard support  150  is installed. The ladder and walkboard support  150  may be installed in this fashion from outside or inside a scaffold frame. 
         [0021]    As shown in  FIG. 2 , a second ladder and walkboard support  150  may be installed in the opposite open side  110 , providing a means for supporting walkboards  114  on intermediate ladder rungs  302 . Each ladder and walkboard support may also serve as a ladder to allow workers to ascend a tall scaffold. 
         [0022]    Although weight tends to lock an installed ladder and walkboard support in place, an installed ladder and walkboard support may be further secured with security pins.  FIG. 5  shows a pin  500  with an attached retainer  502 . Once a hook  304  is suspended from an upper scaffold rung  108 , the retainer  502  is bent to allow the pin  500  to pass through holes  504  in the hook  304  that are positioned below the scaffold rung  108 . The retainer  502  is then allowed to return to its normal form and is hooked around the free end of the pin  500  in the manner shown in  FIG. 6 . For clarity,  FIGS. 2 ,  5 , and  6  show hooks separated from engaged upper rungs, but in use each hook would be contacting and suspended from a rung when installed. 
         [0023]    The principles, embodiments, and modes of operation of the present invention have been set forth in the foregoing specification. The embodiments disclosed herein should be interpreted as illustrating the present invention and not as restricting it. The foregoing disclosure is not intended to limit the range of equivalent structure available to a person of ordinary skill in the art in any way, but rather to expand the range of equivalent structures in ways not previously contemplated. Numerous variations and changes can be made to the foregoing illustrative embodiments without departing from the scope and spirit of the present invention.

Summary:
A ladder and walkboard support is installed within an open side of a construction scaffold, providing additional support rungs within the open side. The support has upper hooks that hang from an upper scaffold rung and lower saddles that engage the vertical surfaces of a lower scaffold rung, preventing the lower end of the support from swinging when installed. Walkboards may span a pair of supports installed in opposing open sides.