referring now to the drawings in detail , fig1 shows a clamping apparatus 100 for clamping optical elements such as lenses . in a first embodiment , the optical elements are lenses 50 . the clamping apparatus 100 includes a first fixture 10 , a second fixture 20 , and two mounting members 30 . the first fixture 10 and the second fixture 20 are both attached to the two mounting members 30 so as to clamp a plurality of lenses 50 in an adjustable manner . referring together to fig2 , the first fixture 10 is an elongated bar with a substantially rectangular cross section , including a holding surface 11 and two sliding portions 12 . the first fixture 101 has a plurality of holding holes 110 evenly defined in the holding surface 11 , and each of the holding holes has a shape corresponding to one of the lenses 50 . a fringe portion ( not labeled ) of each lens 50 can be partly received in one of the holding holes 110 . one of the sliding portions 12 extends from one end of the first fixture 10 , and the other extends from an opposite end of the first fixture 10 . referring together to fig3 , the second fixture 20 includes a bar portion 21 and two extending portions 22 . the bar portion 21 evenly defines a plurality of holding grooves 210 corresponding to plurality of holding holes 110 of the first fixture 10 . the bar portion 21 has two end walls ( not labeled ) and each of the end walls defines a mounting hole 23 , and the mounting hole 23 is a screw thread hole . each of the extending portions 22 is substantially rectangular in shape . one of the extending portions 22 extends from one end of the bar potion 210 , and the other extends from an opposite end of the bar potion 210 . the mounting members 30 are substantially rectangular in shape . each of the mounting members 30 defines a guiding groove 31 , a sliding groove 32 , and a fixing hole 33 . the guiding groove 31 is arc - shaped and is defined in a corner of the mounting member 30 . the sliding groove 32 is a rectangular groove defined in an end portion of the mounting member 30 . the fixing hole 33 is a screw thread hole defined adjacent to the sliding groove 32 . in assembly , one of the sliding portions 12 of first fixture 10 is movably received in the guiding groove 31 of one of the mounting members 30 . one of the extending portions 22 of the second fixture 20 is received in the sliding groove 32 of one of the mounting members 30 . the other one of the sliding portions 12 of first fixture 10 is movably received in the guiding groove 31 of the other one of the mounting members 30 . the other one of the extending portions 22 of the second fixture 20 is received in the sliding groove 32 of the other one of the mounting members 30 . the sliding portions 12 of the second fixture 12 are moved to one end of the sliding groove 32 , and each of the fixing holes 33 in the mounting member 30 is aimed at each of the mounting holes 23 in the second fixture 20 at such a position . by using two bolts ( not shown ) engaging in the mounting holes 23 and the fixing hole 33 , the second fixture 20 is fixed to the mounting members 30 . after assembly , the mounting members 30 are parallel to each other , and the first fixture 10 and the second fixture 20 can be adjusted between the two the mounting , members 30 . referring together to fig4 - 6 , the clamping apparatus 100 is used in a method to clean lenses 50 . the method for washing lenses 50 includes the following steps . the first fixture 10 is adjusted so that the sliding portions 12 of first fixture 10 are moved to one end of the guiding groove 31 , and the holding holes 110 of the first fixture 10 face the holding grooves 210 of the second fixture 20 . the lenses 50 are put into the holding grooves 210 , and each of the lenses 50 is partly received in each of the holding grooves 210 . the second fixture 20 is moved along the sliding groove 32 towards the first fixture 10 so that each of the lenses 50 is also partly received in each of the holding holes 11 , then the lenses 50 are fixed between the first fixture 10 and the second fixture 20 . by using two bolts engaging in the mounting holes 23 and the fixing hole 33 , the second fixture 20 is fixed to the mounting members 30 for stopping the lenses 50 from falling off the clamping apparatus 100 . the clamping apparatus 100 with the lenses 50 are immersed into a washing liquid for washing . the first fixture 10 is moved together with the lenses 50 along the guiding grooves 31 of the mounting members 30 , thus the position of the lenses 50 is adjustable according to different requirements and the lenses 50 are effectively cleaned . the clamping apparatus 100 is then taken out of the liquid . the first fixture 10 is adjusted so that the holding holes 110 of the first fixture 10 again face the holding grooves 210 of the second fixture 20 . the second fixture 12 is disengaged from the mounting members 30 by disassembling the two bolts from the mounting holes 23 and the fixing hole 33 . the second fixture 12 is moved along sliding groove 32 to one end for taking out the lenses 50 from the clamping apparatus 100 . in a second embodiment , referring together to fig7 , two mounting members 200 each define a plurality of guiding grooves 201 , a plurality of sliding grooves 202 and a plurality of fixing holes 203 . therefore , each of the mounting members 200 are able to mount a plurality of first fixtures 300 and a plurality of second fixtures 400 so that the efficiency for washing lenses 500 is further improved . it is to be understood , the clamping apparatus can only have one mounting member or a plurality of mounting members . it is to be understood , however , that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description , together with details of the structures and functions of the embodiments , the disclosure is illustrative only , and changes may be made in detail , especially in matters of shape , size , and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed .