the context excludes that possibility the term u201c at least u201d 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 u201c at least 1 u201d means 1 or more than 1 the term u201c at most u201d 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 u201c at most 4 u201d means 4 or less than 4 and u201c at most 40 u201d means 40 or less than 40 when in this specification a range is given as u201c a first number to a second number u201d or u201c a first number a second number u201d 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 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 u201c open u201d side of a scaffold frame as shown in fig1 a typical scaffold frame 100 as is known.