Some bottom bracket sets include a plastic sleeve to keep crud out of the bearing. Any screw, rivet, stud, etc. used to hold that guide should be short enough to not interfere with insertion or removal of the sleeve.
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My C&V Bikes:
1972 Bottecchia Professional, 1972 Legnano Olympiade Record,
1982 Colnago Super, 1987 Bottecchia Team C-Record,
1988 Pinarello Montello, 1990 Masi Nuova Strada Super Record,
1995 Bianchi Campione d'Italia, 1995 DeBernardi Thron