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 OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to ladders. More particularly, it relates to leveling ladders for use on uneven surfaces. 
     2. The Prior Art 
     The patent to Griffith, U.S. Pat. No. 5,232,067, discloses a stile extending attachment for a ladder. The invention consists of an attachment device for use on a ladder having hollow rungs and two side stile members. A long bolt is inserted through two of the hollow rungs and extending from one side stile through to the other and through the attachment device. The attachment device is releasably fastened by a nut and washer at each of the through bolts, thereby allowing the adjustment of the length of one of the two side stile members of the ladder. 
     The patent to Thocher et al., U.S. Pat. No. 5,273,133, discloses a ladder leveler. The invention consists of a mechanical gear system and extension member. Upon manually rotating the gear mechanism, the side member will extend or retract according to the direction of the rotation. A means for locking the gear system in place is provided. 
     U.S. Pat. No. 5,107,958 to Johnson, discloses a ladder leveler. The invention consists of a pair of leg extensions that are releasably affixed to the end of the side rails of the ladder. The extensions have a tightening bolt and a tension spring to secure the extension at a desired height. The extensions shown, fit over the end of the side rails and can be affixed thereto with screws or the like. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method of leveling a ladder whereby the leveling devices (i.e., leveling legs) are inserted into the end of the hollow side rails of the ladder. The leveling legs are adjustable in height by using a plurality of support holes in the leveling leg and the side rails of the ladder. A plurality of securing bolts, each having a diametrically disposed bore therein for receiving a cotter pin, are used to maintain the leveling leg at a desired height. Once inserted, the cotter pin will secure the bolt in place and thereby secure the leveling leg at the desired height. 
     It is therefore an object of the present invention to provide a ladder leveler that is easily and accurately adjusted. 
     It is another object of the present invention to provide a ladder leveler that can be installed on any ladder having hollow side rails. 
     Yet another object of the invention is to provide a ladder leveler that is reliable and easy to manufacture. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention. 
     In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
     FIG. 1 is a perspective view of the leveling leg of the present invention; 
     FIG. 2 is a side elevational view of the leveling leg of the present invention; 
     FIG. 3 is a front elevational view of the leveling leg of the present invention; 
     FIG. 4 is a schematic view of the ladder and leveling legs of the present invention; 
     FIG. 5 is an elevational view showing the leveling legs used on an uneven surface; 
     FIG. 6 is the securing bolt of the invention; and 
     FIG. 7 is the cotter pin used by the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Turning now in detail to the drawings, FIGS. 1-3 show the ladder leveling leg 10 having a body 12 with an inner side 14 and an outer side 16. A pair of elongated semicylindrical support members 18 and 20 are disposed on inner side 14 of leveling leg 10. A plurality of holes 22a-22e extend through the width of leveling leg 10 from one side to the other. Holes 22a-22e provide a means for adjusting the height of leveling leg 10 when secured within a ladder. The top portion of leveling leg 10 has a U-shaped cutout 40 which allows leveling leg 10 to be inserted into the bottom of the side rails of a ladder and be adjusted so that U-shaped cutout 40 surrounds the lower most rung of the ladder. A second cutout 42 is provided in the curved portion of U-shaped cutout 40 and on the outer side 16 of leveling leg 10. The second cutout 42 can accommodate the fastening means used to secure the lower most rung to the side rails of the ladder. Thus, cutout 42 allows leveling leg 10 to be inserted into the side rail of the ladder without interfering with the fastening means used to affix the lower rung to the ladder. 
     A bore 24, centrally located immediately below cutout 40 and extending through leveling leg 10 from inner side 14 to outer side 16, further secures leveling leg 10 in the desired position within the ladder. A recess 26, concentrically disposed around bore 24, is designed to receive a washer for securing a bolt through securing hole 24. 
     A gripper support hole 28 is provided near the bottom of leveling leg 10 and centrally disposed therein. Gripper hole 28 is used to secure a gripper foot 56 (FIG. 4) to leveling leg 10 to prevent the ladder from slipping. 
     FIG. 4 shows a ladder 50 having side rails 57 and 58 with rungs 52 and 54 therebetween. A plurality of first support holes 25a-25e are disposed in the lower portion of side rails 57 and 58 and extend through said side rails parallel to rungs 52 and 54. A single second support hole 29, disposed in the lower portion of both side rails 57 and 58, extends through said side rails from the front to the back of ladder 50 and perpendicular with respect to rungs 52 and 54. 
     When leveling leg 10 is inserted into the lower end of side rail 57, bore 24 can be aligned with any one of the first support holes 25a-25e depending on the desired height. Once bore 24 is aligned with one of first support holes 25a-25e, one of the plurality of holes 22a-22e on leveling leg 10 will automatically be aligned with second support hole 29 in side rail 57. When the leveling leg is at the desired height, a securing bolt 60 (FIG. 6) is inserted through the respective support holes in side rail 57, of ladder 50, and leveling leg 10 to maintain said leveling leg in a fixed position. A gripper foot 56 is releasably fastened to leveling leg 10 through gripper support hole 28. Gripper foot 56 prevents leveling leg 10 from slipping when placed on the ground. 
     Referring to FIGS. 5-7, leveling leg 10 is shown inserted in side rail 57. A securing bolt 60 has a head 62 and a diametrically disposed bore 64 near the end opposite said head. A cotter pin 70 is used to hold bolt 60 in place after said bolt has been inserted to secure leveling leg 10 in place. Cotter pin 70 has a straight portion 72 and a spring portion 74. Straight portion 72 of cotter pin 70 is inserted into diametrically disposed bore 64 of bolt 60 and spring portion 74 engages bolt 60 to hold cotter pin 70 in place. 
     As shown in FIG. 5, securing bolt 60a is shown passing through support hole 25e in side rail 57 and through bore 24 in leveling leg 10. Cotter pin 70a is shown disposed through diametrically disposed bore 64a (not shown) in bolt 60a, thereby maintaining said bolt in a fixed position. Bolt 60b is shown disposed through second support hole 29 in side rail 57 to further secure leveling leg 10 at the desired height. Gripper boot 56 is releasably fastened to leveling leg 10 using a releasable fastener of any suitable known type. 
     Although leveling leg 10 is shown having a substantially rectangular shape, leveling leg 10 can be of any suitable known shape, such as, for example, cylindrical, oval or elliptical to accommodate a variety of different shaped side rails 
     While one embodiment of the present invention has been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.

Summary:
An apparatus and method of leveling a ladder, having hollow side rails, on an uneven surfaces using at least one leveling device. Support members, support holes and securing bolts maintain the leveling device at a desired height when disposed within the side rail of a ladder. A gripper foot, attached to the leveling device, provides a secure footing for the leveling device and the ladder its connected to.