referring now to various figures of the drawing where like reference numerals refer to like parts there is shown at 20 in fig1 a convertible slip - resistant , attachment device for use on a primary footwear , and which device is constructed in accordance with this invention . the convertible device 20 is arranged to be used , i . e ., worn , on a shoe or boot 10 or any other primary footwear to render it resistant to slippage on ice or snow or other slick surfaces . the boot 10 is shown in phantom in drawings herein , is of conventional construction , and is merely exemplary of any type of primary footwear on which the subject invention can be worn . the boot 10 basically comprises an upper having a toe portion 12 and a heel counter portion 14 . the upper is mounted on a sole assembly having a toe / forefoot / arch portion 16 and a heel portion 18 . the device 20 is preferably an integral or one - piece , sling - type , unit molded from any suitable flexible , resilient material , e . g ., rubber or polyvinyl chloride . by virtue of the flexible , resilient nature of the material making up the unit 20 , it can be stretched to accommodate various sizes and shapes of primary footwear . the unit 20 basically comprises a sole 24 , a toe box 26 , a heel counter box 28 , a pull tab 30 . the details of the toe box and heel counter box will be described later . suffice it for now to state that the toe box is made up of plural straps which extend from respective portions of the sole 24 and merge together above the sole so as to form a hollow interior space into which the toe portion 12 of the upper of the boot 10 can fit to releasably mount the front of the unit 20 thereon . the heel counter box is also made up of plural straps which extend from respective portions of the sole 24 and merge together above the sole so as to form a hollow interior space into which the heel portion 18 of the sole of the boot 10 the contiguous heel counter portion 14 of the upper of the boot can fit to releasably mount the rear of the unit 20 thereon . as should be appreciated by those skilled in the art the flexible , resilient nature of the material making up the unit 20 enables the straps of the toe box and the heel counter box to stretch to accommodate footwear of various sizes and shapes . as can best be seen in fig2 the sole 24 includes plural raised circular cleats 32a - 32d and plural raised ridges 34a and 34b . steel or other hard material spikes 36 are mounted in the cleats and ridges to project outward therefrom . the spikes 36 are arranged to dig into ice , snow or other slick surfaces when the attachment unit 20 is worn on the boot 10 or any other primary footwear , and thereby provide enhanced traction for the wearer . in particular , as can be seen the ridge 34a is of a general x - shape and is located in the underside of the sole of the unit 20 in the toe and contiguous forefoot regions . the circular cleats 32a - 32d are located in the interstices of the crossing portions of the x - shaped ridge 34a . the ridge 34b is of a general u - shape and is located in the underside of the sole of the unit 20 in the heel regions . the arch region of the sole of the unit 20 is open . in particular it includes an opening 38 between the forefoot and heel regions so as to define a pair of side straps 40 on either side of the longitudinal axis 42 of the unit 20 and which connect the toe / forefoot portion of the unit to the heel portion of the unit . as best seen in fig4 the toe box 26 comprises three straps 44a , 44b , and 44c . the strap 44a projects from the tip or toe of the sole 24 and extends upward and backward therefrom . the strap 44b projects from one side of the sole in the forefoot region adjacent to the arch region and extends upward and forward therefrom at an acute angle to the longitudinal axis 42 to merge with the strap 44a at a junction . in a similar manner the strap 44c projects from the opposite side of the sole in the forefoot region adjacent to the arch region and extends upward and forward therefrom at an acute angle to the longitudinal axis 42 to also merge with the strap 44a at the junction . this arrangement thus forms a hollow interior space between the straps 44a , 44b , and 44c and the inner surface of the sole 24 of the unit 20 to accommodate the toe portion of the boot , as mentioned earlier . as best seen in fig1 and 3 the heel counter box 28 comprises three straps . in particular , one strap 46a projects from the rearmost portion of the sole 24 and extends upward therefrom . another strap 46b projects from one side of the sole in the heel region adjacent to the arch region and extends upward and rearward therefrom at an acute angle to the longitudinal axis 42 to merge with the strap 46a at a junction . in a similar manner a third strap ( not shown ) projects from the opposite side of the sole in the heel region adjacent to the arch region and extends upward and rearward therefrom at an acute angle to the longitudinal axis 42 to also merge with the strap 46a at the junction . this arrangement thus forms a hollow interior space between those straps and the inner surface of the sole 24 of the unit 20 to accommodate the heel counter portion 14 of the boot 10 as mentioned earlier . an opening 48 is provided in the strap 46a to accommodate the rear portion of the heel of the primary footwear as shown in fig1 and 3 . the pull tab 30 extends upward from the junction of the straps heel counter straps to provide a gripping portion to enable the attachment unit to be pulled onto the heel counter of the boot 22 . in order to facilitate the pulling of the attachment unit onto the heel counter , plural stepped ridges 50 are located on the outer surface of the strap 46a and on the pull tab 30 . in order to enable the unit 20 to be converted to a - half - sole type device , the unit includes indicia means defining the boundary or &# 34 ; trim line &# 34 ; of a portion of the sole 24 and contiguous strap which can be removed to form a half - sole unit . the removable portion of the unit 20 is identified by the reference number 54 and basically comprises the heel portion of the sole 24 which includes the u - shaped ridge and associated spikes and the lower portion of the strap 46a . the trim line or indicia basically comprises three generally linear grooves . in particular , a first generally linear , horizontally oriented groove 56a of reduced material thickness is located in the strap 46a immediately below the junction at which the other two straps of the heel counter box merge with it . a second , and angularly oriented linear groove 56b , also of reduced thickness material , is located in the sole 26 immediately below the junction from which the strap 46b extends backward as clearly shown in fig1 . a similar groove ( not shown ) is located in the sole below the junction from which the opposite strap extends backward . these three grooves , plus the rear edge of the sole opening 38 and the lower edges of the two angled straps of the heel counter box define the boundary of the removable portion 54 of the unit . in order to remove the removable portion , a scissors or some other cutting means ( not shown ) can be used to sever the material making up the unit along the trim line grooves . it should be pointed out at this juncture that the use of one or more grooves to establish the boundary or trim line of the removable portion of the unit 20 is not mandatory . thus , any visually perceptible means , e . g ., as a raised ridge , a colored line , etc ., can be used to define the trim line and demarcate boundary of the portion 54 of the unit 20 which is to be severed and removed . in fact , the trim line or indicia need not even be part of the unit 20 itself . thus , it is contemplated the indicia be in the form of written or other recorded instructions describing the portion ( s ) 54 of the unit 20 to be severed or removed . in such a case , all that is required for the user is to follow the written or recorded instructions and trim or remove the removable portion 54 of the unit 20 . in order to expedite the severing or removal of the removable portion of the unit , the boundary of the removable portion of the unit may be weakened , e . g ., the groove perforated , so that the removable portion can be torn away without requiring a scissors or other severing device . in any event once the removable portion 54 of the unit 20 has been removed , the unit can be placed on the boot 10 as shown in fig6 - 8 , whereupon the heel 18 of the boot 10 extends through the opening created by the removal of the removable portion 54 , while the toe portion 12 of the boot is located within the toe box 26 as described earlier . as should be appreciated by those skilled in the art the conversion of the unit 20 of this invention from its full - sole configuration to its half - sole configuration results in the creation of a relatively large opening from the forefoot region of the unit to the rear end of the heel region , i . e ., the area encompassed by the original opening 38 and the portion of the heel which had been removed . thus , the resulting half - sole unit can be used to accommodate various types and sizes of primary footwear which may not have been readily accommodated when the unit was in its full sole configuration , by virtue of the fact that the large opening can receive any size , type or shape of heel . this is particularly true since the device is formed of a resilient material and can readily stretch to further enhance footwear accommodation . without further elaboration the foregoing will so fully illustrate our invention that others may , by applying current or future knowledge , adapt the same for use under various conditions of service .
an convertible , footwear attachment device and methods of configuring it and using it on a primary footwear to provide resistance to slippage on snow , ice or other slick surfaces . the attachment device is of the sling - type , full - sole unit and is formed of an elastic , flexible and severable material . the full - sole unit is made up of a sole , a toe attachment assembly , a heel attachment assembly , and visible indicia , e . g ., grooves , for indicating the boundaries of a removable portion of the full - sole unit which may be severed therefrom to form the half - sole unit . the attachment assemblies enable the device to be releasably mounted on the primary footwear irrespective of whether the device is converted from the full - sole unit to the half - sole unit or not . the sole and heel portions of the full - sole unit each include plural hard , ice - gripping projections , e . g ., spikes .