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Chapter10UsingBlockandExternalReferences10.1OverviewAutoCADprovidesseveralfeaturestohelpyoumanageobjectsinyourdrawings.Withblocksyoucanorganizeandmanipulatemanyobjectsasonecomponent.Youcanalsoassociateitemsofinformationwiththeblocksinyourdrawings-forexample,partnumbersandprices-byattachingattributes.Specificationsheetsorbillsofmaterialscanbecreatedusingthisinformation.YoucanattachoroverlayentiredrawingsinyourcurrentdrawingbyusingAutoCADexternalreferences,orxrefs.Whenyouopenadrawingthatcontainsxrefs,anychangesthathavebeenmadeinthereferenceddrawingappearinthecurrentdrawing.10.2WorkingwithBlocksAblockisacollectionofobjectsyoucanassociatetogethertoformasingleobject,orblockdefinition.Youcaninsert,scale,androtateablockinadrawing.Youcanexplodeablockintoitscomponentobjects,modifythem,andredefinetheblock.AutoCADupdatesallcurrentandfutureinstancesofthatblockbasedontheblockdefinition.Blocksstreamlinethedrawingprocess.Forexample,youcanuseblockstoBuildastandardlibraryoffrequentlyusedsymbols,components,orstandardparts.Youcaninsertthesameblocknumeroustimesinsteadofre-creatingthedrawingelementseachtime.Revisedrawingsefficientlybyinserting,relocating,andcopyingblocksascomponentsratherthanindividualgeometricobjects.Savediskspacebystoringallreferencestothesameblockasoneblockdefinitioninthedrawingdatabase.Forinformationabouthowtocreateablock,see"DefiningBlocks."Whenyouinsertablockinyourdrawing,youarecreatingablockinstance.Eachtimeyouinsertablockinstance,youassignascalefactorandrotationangletotheinsertedblock.Youcanalsoscaleablockinstanceusingdifferentvaluesinanycoordinate(X,Y,Z)direction.Blocksmakeitpossibleforyoutoorganizeyourdrawingtasksinasystematicway,sothatyoucansetup,redesign,andsorttheobjectsinyourdrawingsandtheinformationassociatedwiththem.DefiningBlocksYoucangroupobjectstocreateblockdefinitionsinthecurrentdrawing,oryoucansavetheblockasaseparatedrawingfile.Whenyoudefineablock,youspecifythebasepoint,theobjectstogroup,andwhethertoretainordeletetheobjectsorconvertthemtoablockinthecurrentdrawing.YoucanalsoenteratextdescriptionandspecifyaniconusedtohelpidentifytheblockdefinitioninAutoCADDesignCenter.Blockdefinitionsareoneofmanynongraphicalobjectssavedinadrawing.See"WorkingwithNamedObjects."Tocreateablockdefinition1FromtheDrawmenu,chooseBlockMake.2IntheBlockDefinitiondialogbox,enteranamefortheblock.3UnderObjects,choosetheSelectObjectsbuttontousethepointingdevicetoselectobjectsfortheblockdefinition.Thedialogboxclosestemporarilywhileyouselectobjectsfortheblock.PressENTERwhenyouaredoneselectingblocks.Thedialogboxreopens.4Ifyouwanttocreateaselectionset,usetheQuickSelectbuttontocreateordefineafilterforyourselectionset.See"FilteringSelectionSets."5UnderObjects,specifywhethertoretain,converttoablock,ordeletetheselectedobjects.Retain:Keepsselectedobjectsinthecurrentdrawing,intheiroriginalstate.ConverttoBlock:Replacesselectedobjectswithaninstanceoftheblock.Delete:Removesselectedobjectsaftertheblockisdefined.6UnderBasePoint,enterthecoordinatevaluesfortheinsertionbasepointorchoosetheSpecifyInsertionBasePointbuttontousethepointingdevice.7UnderDescription,entertexttohelpidentifytheblockforeasyretrieval.8UnderIcon,specifywhethertocreateaniconfromtheblockdefinition.Donotincludeanicon:Omitspreviewimagefromblockdefinition.Createiconfromblockgeometry:Savespreviewimagewiththeblockdefinition.9ChooseOK.Thebl...